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Working Paper 92 18

THE DETERMINANTS OF AIRPORT HUB LOCATIONS,
SERVICE, AND COMPETITION

v

by Neil Bania, Paul W. Bauer,
and Thomas J. Zlatoper

Neil Bania is the research director of the
Mandel Center for Non-Profit Organizations at
Case Western Reserve University, Cleveland;
Paul W. Bauer is an econo~nistat the Federal
Reserve Bank of Cleveland; and Thomas J.
Zlatoper is an associate professor of economics
at John Carroll University, University Heights,
Ohio, and a research associate at the Center
for Regional Economic Issues at Case Western
Reserve University.
Working papers of the Federal Reserve Bank of
Cleveland are preliminary materials circulated
to stimulate discussion and critical comment.
The views stated herein are those of the authors
and not necessarily those of the Federal Reserve
Bank of Cleveland or of the Board of Governors
of the Federal Reserve System.

December 1992

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ABSTRACT

Although the airline industry has been studied extensively since passage of the Airline
Deregulation Act of 1978, relatively little effort has gone into examining how hub location affects
the level of service and degree of competition found at airports in the system. To help close'this
gap, we investigate the geographic distribution of airline hub operations, the level of service, and
the extent of competition at 112 major U.S.airports, extending previous work by Bauer (1987)
and Butler and Huston (1989). Our key innovation is that we derive our measures of service and
competition from indicator matrices that describe each airline's route system.

clevelandfed.org/research/workpaper/index.cfm

Introduction
Many of the changes that have rocked the airline industry since passage of the Airline
Deregulation Act of 1978 have received a great deal of attention from researchers.' The emphasis
has been on the effect of deregulation on airline fares, mergers, and the development of hub-andspoke route systems. Airlines have adopted hub-and-spoke networks to make more efficient use
9

of their equipment--a trend that is exemplified by modification of United Airlines' route structure
between 1965 and 1989 (see figure 1).
Our focus in this paper is somewhat different. We investigate the geographic distribution
of airline hub operations, the level of service, and the extent of competition at major U.S. airports,
extending previous work by Bauer (1987) and Butler and Huston (1989). Instead of using an
aggregate measure of airline service, we utilize a new, comprehensive measure derived from
individual airline route data. We then employ these data to develop and analyze new measures of
competition at individual airports.
The first section of this paper utilizes information on nonstop service from the nation's 112
largest airports to examine the route structure of the 13 major U.S. airlines, to identify the
Section I1 then
location of airline hubs, and to measure the extent of competition at each fa~ility.~
develops a model of hub location, airline service, and concentration. Estimates of this model are
presented in section III, and section IV summarizes our findings.

I. Characteristics of U.S. Airline Service
In this section, we use data on nonstop flights from airports in the nation's 100 largest

'See, for example, Bailey and Williams (1988). Bailey, Graham, and Kaplan (1985). Borenstein (1992). Meyer and
Oster (1987). and Morrison and Winston (1987).
2 ~ h 13
e airlines included in our sample are Alaskan Airlines, American, America West, Braniff, Continental,
Delta, Eastern, Midway, Northwest, Southwest, TWA, United, and USAir. According to the Air Transport
Association (1990). U.S. passenger airlines with 1989 revenues in excess of $100 million per year included these
13 plus Pan American and Piedmont We excluded Pan American because its route structure is primarily
international, while Piedmont's routes were included in USAir's schedule.

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metropolitan areas to determine the location of airport hubs.3 We choose to rely on our data
rather than statements from the airlines because this allows us to impose uniform standards across
carriers. In addition, we develop new airport- and route-based measures of industry
concentration, which are used as dependent variables in the model discussed in section II.

Data
Our sample consists.ofthe airports, served by the major carriers, in the 100 most.populous
Metropolitan Statistical Areas (MSAs) in 1987.4 Because some of these regions contain more
than one airport, a total of 112 facilities are incl~ded.~
Our data set indicates whether an airline serves a particular route, but provides no
Thus, neither the level of actual activity nor passenger
information about flight freq~ency.~
enplanements are captured. Still, we do have detail on routes and airlines not available in other
data sets.7 We exploit the service data by airline and destination to compute measures of
competition based on both overall service and route-by-route information.
While it is well known that most airlines have adopted some form of hub-and-spoke

3~ more extensive description of the data and a detailed analysis of each airline's route stnrcture'k be found in
Bania, Bauer, and Zlatoper (1992).

4 ~ used
e the Office of Management and Budget's 1988 deftnition of MSAs to form the list of qu.alifying regions.
SManyof the nation's largest MSAs are adjacent to another MSA (such as New York City and Newark, NJ). In
such a case, the second MSA may contain another airport that is a potential substitute; however, even without a
second airport, the combined economic activity of the two MSAs creates a greater demand for air service. Thus,
we combined MSAs into larger metropolitan areas according to the Officeof Management and Budget's 1988
definition of Consolidated Metropolitan Statistical Areas (CMSAs). This resulted in 10 metropolitan areas with
multiple airports (a total of 26 airports). See table 1 for a complete listing.
6The sample includes a total of 12,432 possible routes. However. we collected data for only half of these and
assumed that service was symmetric. For example, we held that if an airline serviced the Portland-Atlanta route,
then it also serviced the Atlanta-Portland route. To check this, we selected one airline (American) and collected
data for routes in both directions. The symmetry assumption was valid in all but one case.

o or

example, Bauer (1987) includes data on passenger enplanements by airport, but contains no destination or
airline-specific information.

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system, the determination of what constitutes a hub is not straightforward.8 Our approach is to
construct, for each airline and airport combination, an index of hub activity that measures the
degree to which that airport is connected to the rest of an airline's network. For an airport-airline
combination, the index is the percentage of other airports in the airline's route system that can be
reached via nonstop service. Hub locations are well connected to an airline's network, while
spoke airports are not. In a hub-and-spoke network, we would expect to find only a small
number of airports that are well connected, many that are not well connected, and few in between.
Thus, the distribution of the hub index should be bimodal, with a large spike at low service levels
(low hub-index values) and a much smaller spike at higher levels (high hub-index values). On the

j

other hand, if an airline does not use a hub-and-spoke system, we would expect to find a relatively
steady decline in the distribution of the hub index.

Hub Locations
To determine hub locations, we examined the hub-index distributions for each airline
(displayed in figure 2). We found that in almost all cases, the hub locations were easily identified,
since, as expected, very few had high service levels, a large number had extremely low levels, and
few fell in the middle. The exceptions were the relatively diffuse carriers, USAir, Alaskan
Airlines, and Southwest. These airlines do concentrate their activity in a small number of airports,
but there is a relatively steady decline in the hub-index distribution. Thus, determining the lower
bound of what constitutes hub service for them is somewhat more difficult. For these airlines, we
arbitrarily designated airports with higher levels of service as hubs.9
Table 2 reports the 44 airport-airline combinations that we classified as hub locations.
*~esearchershave taken several approaches to defining hubs. The Federal Aviation Administration (FAA) looks
at total passenger hoardings. while Butler and Huston (1989) use a functional definition of a hub as an "airponat
which large blocks of incoming and outgoing flights are coordinated to create numerous potential connections."
Our definition is also a functional one, based on an analysis of each airline's route structure.

g ~ hlower
e
bound varied across airlines primarily because of airline size differences. In small route networks, high
hub-index values are easier to obtain, larger airlines showed much greater variety in the size of their hubs.

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This list represents only 35 airports, since some of these have more than one airline with hub
activity. Column 3 reports the total number of airports in the sample served by a given airline,
column 4 is the number of those airports that can be reached with a nonstop flight, and column 5
is the number that can be reached with a one-stop flight.

a

Most airports served by a given airline can be reached via a nonstop or a one-stop flight
from the hub airports. This can be seen by comparing the sum of columns 4 and 5 with column 3.
For example, from Cleveland, passengers have nonstop service to 25 of the 71 other airports
served by Continental. Another 44 airports can be reached with one-stop service. The key
variable that we used to classify hubs--the hub index--is contained in column 6. High values
correspond to the relatively small number of well-connected airports in the frequency distributions
displayed in figure 2. The hub index ranges from a high of 100 percent for Midway Airlines at
Chicago idw way airport to a low of 17 percent for United Airlines at Los Angeles International.

Measures of Competition
If the airline industry were perfectly contestable, there would be no point in calculating

any measures of the extegt of competition, since such measures would have no meaning. Because
no one has found that the airline industry meets these conditions--in fact, most studies show that
the more competitors there are on a route, the lower fares tend to be--we construct various
measures of the extent of competition based on the number of carriers offering seivice on a route
or from an airport.10 Our measures do assign a large role for potential competition by treating
infrequent service on a route in the same way as more frequent service.
We computed a measure of the overall degree of competition at each airport by

loseeBailey, Graham, and Kaplan (1985). Bauer and Zlatoper (1989). Borenstein (1989). Call and Keeler (1985),
Hurdle et al. (1989).and Momson and Winston (1987).

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calculating two versions of the Herfiindahl index for both nonstop and one-stop service." In table

3, we report the nonstop and one-stop service levels at each airport in the sample (columns 2 and
3), as well as the nonstop and one-stop Herfindahl index computed on the basis of overall service
from an airport (columns 4 and 5). These measures are sensitive only to the level of service, not
to the destination. The formula is

where nroutesijis the number of nonstop routes from airport i for the jm airline.12 A similar
measure (Hl,) was calculated for one-stop routes.
The main limitation of these measures is that they are not destination sensitive. For
example, suppose an airport has 10 airlines each serving a different nonstop route. The
Herfindahl index for this airport will be equal to its theoretical minimum for 10 carriers (1,000),
even though there is no nonstop competition at the route level. Although these airlines are not
competing directly at the route level, the presence of other airlines at a given airport represents
potential competition in that providing new service on a given route is easier if an airline already
has gate space. Thus, while this measure is not sensitive to the actual destinations of flights
departing from a given airport, it does measure the potential competition posed by other airlines
serving the same facility. This is an important distinction, because while deregulation has freed
airlines to provide service on any route, acquiring gate space may be difficult or impossible at
some airports.
An alternative measure of airport-level competition that is more sensitive to the actual
l ~ h one-stop
e
calculation involved an aggregation of the nonstop and one-stop data, since we consider nonstop
flights to be competition for one-stop flights. We applied this same principle to all of the one-stop measures of
competition discussed herein.
12'T'he Herfindahl index is a measure of concentration, with larger values corresponding to greater concentration
and therefore less competition. For a more detailed description of this measure, see Koch (1980). pp. 179-80.

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level of competition on a route-by-route basis can be computed using another version of the
Herfindahl index, calculated as

where dserviceij, is one if the jh airline flies the route from i to k, and zero otherwise. HHO, is
the nonstop Herfindahl index for the route between airport i and airport k. To get an overall
measure for each airport (HHO,), we used the unweighted average of HHO, computed over all
routes k. A similar measure (HH1,) was calculated for one-stop connections. The results are
reported in table 3, columns 6 and 7.
This route-by-route Herfindahl measure has two main limitations. First, while it is
sensitive to route patterns of competition, it is not sensitive to the actual level of service (as
measured by the number of airports that can be reached with a nonstop connection). Thus, an
airport with 10 carriers all serving the same nonstop route would have an HE30 value of 1,000-indicating a great deal of competition--even though the facility is not well connected to other
cities. A second problem is that this measure misses potential competition from other carriers
currently serving different routes at the same airport. For example, an airport having 10 carriers
each serving a different nonstop route would have a Herfindahl index equal to its maximum value
(10,000), indicating the absence of competition.
Although a Herfindahl index of 3,200 would be considered very high in most industries
(i.e., the Department of Justice's antimerger guidelines would be violated), there is reason to treat
this as a somewhat moderate level for the airlines. For example, one study finds that air fares
cease to fall once three caniers are serving a route--equivalent to a Herfindahl index of about
3,200 using our definitions.13

13SeeBauer and Zlatoper (1989).

I
I

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In general, three patterns emerge from the Herfindahl indexes. First, one-stop competition
is much greater than nonstop competition, whether airport- or route-based measures are
employed.14 Second, the route-by-route measures indicate much less competition than do the
overall indexes. Finally, the coefficients of variation indicate that there is much more fluctuation

-

in the level of competition for one-stop routes than for nonstop routes.

11. Model of Hub Location, Airport Service, and Competition

Here, we investigate what factors influence hub location, the level of service provided to
an airport, and the degree of competition at each facility. A three-equation model of activity at an
airport can be written as

where H is a measure indicating whether an airport serves as a hub, S is the level of sewice, and C
is the level of competition. Equation (1) is similar to the hub equation specified in B-auer (1987)
and Huston and Butler (1990), while equations (2) and (3) are introduced here. The presence of a
hub carrier is likely to affect the level of service (S) and concentration (C) independently from the
effect of regional economic activity (R), distance @), airport characteristics (A), and weather

(W). Therefore, equations (2) and (3) are not part of a structural model and should be viewed as
reduced-form equations. 15
14Strictlyspeaking, the one-stop Herfidahl index is bounded from above by the nonstop index, since we treat
nonstop flights as competition for one-stop flights. See footnote 10.
151hereare two possible approaches to this problem. One would be to use the fitted values from the estimation of
equation (1) in equations (2) and (3) (Maddala [1983]). The drawback to this is that the calculation of the standard
e m r s is not straightfomard,due to the nonlinearity of equation (1). An alternative approach is to derive
maximum likelihood estimates. We intend to pursue both of these methods in future work.

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A statistical summary of the variables used in the analysis, with definitions and data
sources for each, appears in table 4. The measure used to approximate S is SERVICE, the
number of airports that can be reached via a nonstop flight on any airline from any given airport
H is represented by HUB, a variable equal to one if an airport has at least one hub carrier. (These
airports are listed in table 2.) Finally, C is approximated by several measures of concentration:
HO, HI, HHO, and HH1 (the Herf'indahl indexes described in section I). The values of these
indexes are presented for all airports in table 3.
The likelihood that an airport will have a hub carrier depends in part on R, a vector of
regional economic activity. Factors such as a larger population (POP), higher per capita income
(INCOME), more business- and tourist-related travel (BUSTOUR), and a greater number of large
corporate headquarters (CORP) increase the demand for air travel and thus should raise the level
of service (S), as well as make the airport a more likely candidate for hub operations.
Our measure of business- and tourist-related travel (BUSTOUR) is constructed by
regressing the log of the sum of employment in hotels (SIC 70) and amusement parks and
recreational services (SIC 79) on the log of population and of per capita income. The residual
from this regression, which captures the extent to which local economic activity is insufficient to
support employment in SICS70 and 79, can therefore be viewed as a gauge of business and
tourist travel to a given airport.16

16Theregression is

log (EMW(kEMP79) = 15.4 + 0.89 log(P0P) + 1.27 log(INCOME),
(2.92) (0.04)
(0.34)
where EMP70 is employment in hotels (SIC 70) and EMF79 is employment in amusement parks and recreational
services (SIC 79). The adjusted r-squared is 0.89, and the standard errors appear in parentheses. All three
coefficients are significant at the 1 percent level. The three airports with the largest residual from this regression
are Las Vegas, Orlando, and Daytona Beach The three with the smallest residuals are Toledo, Fremo, and
Dayton. By construction, the residual represents the portion of business and tourist travel that is unrelated to either
population or income. For example, some portion of tourist travel to New Yo* City is related to characteristics of
the city that stem in part from its large population and high income (such as myriad restaurants and culWal
events). This stands in contrast to tourist travel to Orlando or Las Vegas, most of which is probably not related to
population or income.

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In the absence of hubbing activity, concentration should fall with increases in POP,
INCOME, BUSTOUR, and COW. However, hub networks by their very nature increase the
concentration of nonstop flights, since most airports do not have a broad enough economic base

.

to support even one hub carrier with only local traffic. As a result, hub carriers tend to dominate
these airports' nonstop flights. One-stop flights should be much less concentrated, hecause
passengers can use one leg of their flight to reach a competing hub.17
The distance variable, D, is a measure of the central location of an airport. For each
airline, we measured the sum of 2ir miles from each airport to every other airport in that .airline's
route network.18 Airports in favorable locations (smaller D values) are more likely to have hub
carriers and to receive more service. Concentration could be affected by hubbing activity, as
discussed above. In the absence of hubbing activity, a better location would be expected to
support more competition. However, if an airport has a hub airline, its presence may intimidate
other carriers, since they would find it harder to compete with the hub carrier's more frequent
nonstop flights.
A is a vector of regional factors that differentiate airports. Specific components include
SLOT, OTHER, MINOR, and GATEWAY. SLOT is equal to one if an airport faces FAA
restrictions on the number of takeoff and landing slots. Only four facilities have a value of one:
John F. Kennedy International, La Guardia, Chicago O'Hare, and Washington National. If access
to these airports were not limited, carriers would offer more service and would be more likely to
set up hub-and-spoke operations. Concentration might then be higher because of the barrier to
entry, or lower because regulators act to discourage concentration.
OTHER indicates the presence of mother airport in a given airport's economic region.

17wedo not present results for two-or-more-stopflights because they closely mirror those for the one-stop routes.
18wealso tried three other measures of distance: the sum of miles between a given airport and every other
destination, weighted by the population of each destination; the sum of the natural log of miles between airports;
and the sum of the natural log of miles between abports, weighted by the population of the destination. Each of
these measures performed similarly to those reported here.

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For example, Cleveland Hopkins and Akron Canton Regional would both have a value of OTHER
equal to one. MINOR, on the other hand, indicates that the airport has significantly

less capacity

in terms of ground and flight facilities than others in its region. To continue our above example,
Cleveland Hopkins would have a MINOR value equal to zero, while Akron Canton Regional
would have a value equal to one.I9 Finally, GATEWAY indikates whether an airport has
international nonstop connections to Europe, Asia, or the South Pacific.

W is a vector of weather-related variables. Good flying conditions should result in more
service and thus a greater probability of having a hub carrier. To the extent that the weather is
worse for flying, concentration may be higher. To control for these possible effects, we obtained
data on the average number of days per year during which snowfall exceeded one inch (SNOW)
for each airport, as well as on the number of days per year that fog reduced visibility to less than
one-quarter mile (FOG).20

111. Estimation
Using the data discussed above, we estimated equation (1) using logit rather than pr0bit.~1
The two techniques yield similar results, but the disturbance in the logit model allows for more
outliers in the error term. Equations (2) and (3) were estimated in log linear form.

19,41thoughwe defined this variable in a rather ad hoc way, our approach is equivalent to estimating the service
equation with individual airport dummies for airports in regions having more than one facility, and then assigning
MINOR to equal one when the coefficienton the airport dummy is significantly less than the coefficients for other
airports in the region. The values of OTHER and MINOR for metropolitan areas with multiple airports are listed
in table 1.
20rhe weather variables were divided by 365 so that they represented the portion of the year affected by these two
conditions.
21~ecausethe determinants of hub location, air service, and competition in Alaska and Hawaii are likely to differ
from those for airports in the continental United States, all of the equations were estimated both with and without
the Honolulu and Anchorage airports. We report regressions only for the sample excluding these two cities. since
the results are similar.

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Hub Determinants
Table 5 presents the regression results for the various models. We found that four factors
increase the likelihood of an airport's having a hub carrier: a larger regional population, a better
location (a lower D value), gateway connections to Europe, Asia, or the South Pacific, and more
v

business and tourist travel. The effect of each of the remaining variables was statistically
insignificant.
Table 6 ranks the airports by their estimated likelihood of having a hub carrier. The most
likely new hubs based on these results are Miami International, Boston's Logan International,
New York's La Guardia, New Orleans International, and Louisville. The least likely existing hubs
are Washington National, Charlotte/Douglas International, Dayton International, Dallas Love
Field, and El Paso International. It is worth noting that two of these unlikely hubs are associated
with Southwest, a relatively small regional carrier. Southwestis the only airline operating out of
. .

Dallas Love Field and is the dominant carrier operating out of El Paso International. Another of
the unlikely hubs, Dayton International, has since lost hub service from USAir.

Service Determinants
Ordinary least squares (OLS) estimates of.the service regression are presented in table 5.
The results indicate that SERVICE rises less than proportionally with population and falls as
location worsens (distance to other airports increases). The effect of per capita income is positive
but statistically insignificant. Both OTHER and MINOR have a negative and statistically
significant effect, with their magnitudes implying that the presence of another airport in the region
lowers SERVICE 34 percent for nonMINOR airports and 72 percent for MINOR airports.
International connections (GATEWAY) have a positive and significant effect, increasing
SERVICE by 34 percent. Finally, the effect of business and tourist travel (BUSTOUR) is positive
and statistically significant. With the exception of SNOW, the remaining variables have the
expected sign, although none is statistically significant.

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i
Concentration Determinants

Table 5 also presents OLS estimates of the determinants of concentration at both the
airport and route levels for nonstop and one-stop flights, using measures derived earlier. For
nonstop flights and the airport-level concentration measures, the results indicate that a less central
'1

location reduces concentration. While somewhat counterintuitive, this could be a result of
airlines' reluctance to compete head to head with nonstop flights. Under these circumstances, the
more distant airports, which are less likely to be hubs, will have lower nonstop measures of
concentration. Two 'other statistically significant factors are h4INOR and GATEWAY, which
result in higher concentrations (84 percent and 52 percent, respe~tively).~~

<

For route-level measures of concentration, the results for nonstop flights are qualitatively
consistent with those for the airport-level measures. A worse location is associated with lower
concentration levels, although the magnitude of the effect is smaller. MINOR airports have
higher concentration levels, but the effect is only marginally significant. The effect of the presence
of gateway connections is not statistically significant.
We find much more explanatory power, using either measure of concentration, for the
one-stop equations. For such service, the results using airport-level measures indicate that
concentration falls with population and business- and tourist-related activity, but rises for MINOR
airports. Unexpectedly, FOG is associated with higher concentration levels, although the effect is
only marginally sigmficant.
Using route-level measures, we find that population, income, and a better location
decrease concentration, while the presence of another airport in the region and status as a

MINOR airport tend to be associated with higher concentration levels.
An apparent paradox is that central location lowers concentration for one-stop routes, but
raises it for nonstop routes. If an airport has a favorable location, it is more likely to be a hub and

%f course, concentration should be measured at the regional level if one is interested in determining how much

control over fares carriers might have.

I

I

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to have highly concentrated nonstop service, because hub caniers tend to dominate service at
their airports. But having a favorable location also means that other airlines (with hubs at other
airports) will offer at least some service. Consequently, one-stop concentrations tend to be lower
as a result of interhub competition.
\

IV. Summary
We use route-level data to develop measures of the degree to which airlines employ a huband-spoke route structure, and explicitly identify the location of airline hub activity using a new
approach. Our data set allows us to develop airport- and route-specific measures of concentration
that indicate a great deal of variance, particularly at the nonstop level. This is true even among
airports having hub carriers.
We find that the location of airline hub activity is positively related to population and
negatively related to distance from other airports. Regions that have access to international flights
and that are desirable business and tourist destinations are also more likely to have hub caniers.
On the other hand, weather conditions, the presence of large corporate headquarters, per capita
income, and airport slot restrictions play a very small role.
Our findings also show that service (as measured by the number of nonstop connections
from a given airport) increases with population, favorable location, business- and tourist-related
activities, and access to international flights. The presence of multiple airports in a metropolitan
region tends to have just the opposite effect, as do weather, corporate headquarters, per capita
income, and airport slot restrictions.
The results concerning the degree of competition are mixed, depending on the particular
measure employed and whether the unit of analysis is nonstop or one-stop connections. The only
consistent result is that concentration is higher at MINOR airports. Airports in more-populous
regions that are frequented by business travelers and tourists have lower one-stop concentration
measures; however, these factors do not appear to affect nonstop concentration. A favorable
location lowers one-stop concentration measures, but raises nonstop concentration measures.

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1

One explanation for this phenomenon is that while an airport in a favorable location has a higher
probability of attracting a hub carria that will dominate its nonstop service, it is also more likely

I

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Huston, J.H. and Butler, R.V. "The Location of Airline Hubs," working paper, Trinity University,
May 15,1990.
Koch, J.V., Jndustrial Organization and Prices, 2d ed. Englewood Cliffs, N.J.: Prentice-Hall,
1980.

. .

Maddala, G.S. Limited Deuendent and Oudtanve Variables in Econometri~.Cambridge:
Cambridge University Press, 1983.

clevelandfed.org/research/workpaper/index.cfm

Meyer, J.R. and Oster, C.V. Jr. D e r e g u l a t i o n the Future of
Cambridge, Mass.: MIT Press, 1987.

Travel.

Momson, Steven A. and Winston, Clifford. "Empirical Implications and Tests of the
Contestability Hypothesis," Journalofcono&, 30:1, April 1987, pp. 53-66.
National Oceanic and Atmospheric Administration, Local Climatological Data, 1988.
\

Standard & Poor's Corporation. w
Executives. Volume 1, 1989.

d & Poor's R a t e r of C-ons.

Directors. and

U.S. Department of Commerce, Bureau of Economic Analysis. County personal income computer
tape file, 1987.
U.S. Department of Commerce, Bureau of Economic Analysis. County business patterns
computer tape file, 1987.
U. S. Department of Transportation. Air Carrier S
Summary, Data Bank 6, 1986.

u

. Origin and Destination City Pair

clevelandfed.org/research/workpaper/index.cfm

Figure 1. United Airlines Route Structure, 1965 and 1989
1965

Source:

United Airlines schedule guides, 1965 and summer 1989.

J

clevelandfed.org/research/workpaper/index.cfm

Figure 2.

Distribution of Nonstop Service by Airline and A i r p o ~ t

AU Airlines

Air Alaska

American

America West

Braniff

Continental

Delta

Eastern

Midway

Northwest

Southwest

'IWA

United

USAir

Source: Various airline schedule guides, 1989, and authors' calculations.

Note: The maximum value on the vertical axis is 20 airports. and the height of
the bars represenls the number of airports with values of the hub index
falling into the following eight categories: less than 0.1.
0.1-0.2,0.2-0.3.0.3-0.4,0.4-0.5,0.5-0.6,0.6-0.7, andlarger
than 0.7. Each of the airlines had very large number of airpons
with a hub index of less than 0.1: however, the height of the first bar
in each graph was truncated at 20 airports to improve the resolution
of the data for airpons with higher values of the hub index. Data
in the first panel, which represents the composite of all airlines,
is truncated for the f i t two categories. There are 37 airpow
with a hub index less than 0.1 and 35 airports with a hub index
between 0.1 and 0.2.

clevelandfed.org/research/workpaper/index.cfm

Table 1. Metropolitan Areas with Multiple Airports
Metropolitan Area

Airport

Chicago-Gary-Lake County, IL-IN-WI CMSA

Chicago Midway
Chicago O'Hare

Cleveland-Akron-Lorain, OH CMSA

Akron Canton Regional
Cleveland Hopkins International

Dallas-Fort Worth, TX CMSA

OTHER

MINOR

Dallas Love Field
Dallas Ft. Worth International

1
1

1
0

Houston-Galveston-Brazoria,TX CMSA

W i a m P. Hobby
Houston Intercontinental

1
1

0
0

CA CMSA
Los ~n~eles-~naheim-~iverside,

Burbank-GlendalePasadena
Los Angeles International
Long Beach
Ontario International
John Wayne Airport

1
1
1
1
1

1
0
1
1
1

Miami-Fort Lauderdale, FL CMSA

Fort Lauderdale
Miami International

New York-N. New Jersey-Long Island, NY-NJ-CT CMSA

Long Island MacArthur
Newark International
John F. Ke~nedyInternational
La Guardia

1
1
1
1

San Francisco-Oakland-San Jose, CA CMSA

Metropolitan Oakland
San Francisco International
San Jose International

1
1
1

Tampa-St. Petersburg-Clearwater. FL MSA

St. Petersburg-Clearwater
Tampa International

.. 1

Washington, DC-MPVA MSA

Washington National Airport
Washington Dulles Airport

-

\

Source: Authors' assignments.

1

"

1
1

clevelandfed.org/research/workpaper/index.cfm

Table 2. Selected Statistics for Hub Airport-Airline Combinations

'\

4

Metropolitan Area
[I1

Airline

Atlanta, GA MSA
Atlanta,GAMSA
Baltimore. MD MSA
Charlotte-Gastonia-Rock Hill,NC-SC MSA
Chicago-Gary-Lake County, L I N - W I CMSA (Midway)
Chicago-Gary-Lake County. L I N - W I CMSA (O'Hare)
Chicago-Gary-Lake County. L I N - W I CMSA (O'Hare)
Cincinnati-Hamilton, OH-KY-IN CMSA
Cleveland-Alcron-Lorain, OH CMSA ( H o p k h International)
Cleveland-Akron-Lorain, OH CMSA ( H o p k h International)
Dallas-Ft. Worth, TX CMSA (International)
Dallas-Ft. Worth, TX CMSA (International)
Dallas-Ft. Worth, TX CMSA (Love Field)
Dayton-Springfield, OH MSA
Denver-Boulder, CO CMSA
Denver-Boulder, CO CMSA
Detroit-AM Arbor, MI CMSA
El Paso, TX MSA
Houston-Galveston-Brazoria,TX CMSA (Hobby)
Houston-Galveston-Brazoria,TX CMSA (Intercontinental)
Indianapolis, IN MSA
Kansas City, MO-KS MSA
Las Vegas. NV MSA
Los Angeles-Anaheim-Riverside,CA CMSA (LA International)
Los Angeles-Anaheim-Riverside,
CA CMSA (LA International)
Los Angeles-Anaheim-Riverside,CA CMSA (LA International)
Memphis, TN-AR-MS MSA
Minneapolis-St. Paul MN-WI MSA
Nashville, TN MSA
New York-N. NJ-Long Island, NY-NJ-CT CMSA (JFK)
New York-N. NJ-Long Island, NY-NJ-CT CMSA (Newark)
Orlando. FL MSA
Philadelphia-Wilmington-Trenton.PA-NJ-DE-MD CMSA
Phoenix, AZ MSA
Phoenix, AZ MSA
Pittsburgh-Beaver Valley CMSA
Portland-Vancouver. OR-WA CMSA
Raleigh-Durham, NC MSA
Salt Lake City-Ogden, UT MSA
San Francisco-Oakland-San Jose, CA CMSA (SF International)
Seattle-Tacoma, WA CMSA
St. Louis. MO-IL MSA
Washington. DC-MD-VA MSA (Dunes)
Washington, DC-MD-VA MSA (National)

Delta
Eastern
usAir
USAir
Midway
American
United
Delta
Continental
USAir
American
Delta
Southwest
USAir
Continental
United
Northwest
Southwest
Southwest
Continental
usAir
Braniff
America West
Delta
United
USAir
Northwest
Northwest
American
TWA
Continental
Braniff
USAir
America West
Southwest
USAir
Air Alaska
American
Delta
united
Air Alaska
TWA
United
USAir

[21

Source: Various airline service guides, summer 1989, and authors' calculations.

Airports
Hub Service
Served by
Hub
Airline Nonstop One-stop Index
PI
[41
151
[61

Percent
Regional

--

1
7
66
80
76
75
79
60
63
78
72
71
44
50
100
78
72
67
75
70
100
48
81
63
81
75
59
50
68
47
84
69
74
83
86
82
88
64
100
92
80
60
100
50
75
81

I

1

clevelandfed.org/research/workpaper/index.cfm

Table 3. Concentration Statistics lor Airports in Large Metropolitan Areas, 1989

AwJServed by
AU Airlines

Metropolltan Area
111
Albany-Schendy-Troy, NY MSA
Albuquerque. NM MSA
Allentown-Bethlehem, PA-NJ MSA
Anchorage. AK MSA
Atlanta. GA MSA
Augusta, GA-SC MSA
Austin. TX MSA
Baltimore, MD MSA
Baton Rouge. LA MSA
B u r g h a m , AL MSA
Boston-Lawrence-Salm-Lowell-Brohn.
MA NECMA
Buffalo-Niagarq NY CMSA
Charleston. SC MSA
Charleston. WV MSA
Charlotte-Gastonia-Rod; Hill, NCSC MSA
Chananooga. TN MSA
Chicagdjary-Lake County, IL-IN-WI CMSA (Midway)
Chicago-Gary-Lake County, L I N - W I CMSA (O'Hare)
Cincinnati-Hamilton. OH-KY-IN CMSA
Cleveland-&on-Lorain, OH CMSA (Akron-Canton)
Cleveland-Won-Lorain, OH CMSA (Hopkins)
Colorado Springs. CO MSA
Columbia, SC MSA
Columbus, OH MSA
Corpus Christi, TX MSA
Dallas-Fort Worth. TX CMSA (Intmdonal)
Dallas-Fort Worth. TX CMSA (Love Field)
Daytona Beach, FL MSA
Dayton-Springfield. OH MSA
Denver-Boulder. CO CMSA
Des Moines. IA MSA
Detroit-Ann Arbor. MI CMSA
El Paso. TX MSA
Evansville. IN-KY MSA
Fayetteville, NC MSA
Fort Myers-Cape Coral, FL MSA
Fort Wayne. IN MSA
Fresno. CA MSA
Grand Rapids. MI MSA
Greensboro-Winston-Salem-High PoinI. NC MSA
Greenville-Spartanburg. SC MSA
Harrisburg-Lebanon-Carlisle.
PA MSA
Honolulu. HI MSA
Houston-Galveston-Brazoria,TX CMSA (Hobby)
Houston-Galveston-BrazoriqTX CMSA (Intcmat~onal)
Indianapolis. IN MSA
Jackson. MS MSA
Jacksonville, FL MSA
Kansas City, MO-KS MSA
Knoxville, TN MSA
Las Vegas, NV MSA
Lexington-Fayem, KY MSA
Little Rock-North L i e R o d ; AR MSA
Los Angeles-Anaheim-Riverside, CA CMSA (Burbank)
Los Angeles-Anaheim-Riverside,CA CMSA (John Wayne)
Los Angelcs-Anaheim-Riverside,CA CMSA (LA Intmdonal)
Los Angeles-Anaheim-Riverside,CA CMSA (Long Beach)
Los Angeles-Anaheim-Riverside,CA CMSA (Ontario)
Louisville. KY-IN MSA
Madison. WI MSA

--

Herfindah1 Index
(overall service)

Hufindahl Index
(airport pairs)

Nonstop
121

Onestop
131

Nonstop
141

Onestop
151

Nonstop
[a1

One-stop
171

16
16
8
4
84
1
13
47
7
17
43
19
14
9
51
6
38
90
53
7
43
9
9
21
4
76
10
7
30
56
8
60
14
8
8
23
10
12
9
15
4
12
13
28
52
35
8
20
45
14
40
13
11
13
13
53
13
18
18
6

92
90
99
88
27
83
98
64
95
89
68
90
93
83
60
84
72
21
58
99
68
93
98
88
74
35
49
81
80
55
94
51
90
100
95
87

1.872
1,479
3.333
3.061
3.810
5,000
1.247
3,905
3.125
1,818
1,418
2.986
3.772
4.074

1.398
1.266
2,637
4.056
1.104
5,232
1.417
1.191
2,690
1.710
1,025
1,515
2,166
3.540

7.938
7,292
9.375
8.125
6.538
5.000
7,436
8.652
9,286
8,725
8.109
8.860
8.929
10.000
9.248
9.167
8,969
6,056
9.088
9,286
7.345
8.889
8.889
8.095
10,000
6,086
10.000
8,333
9.833
6,711
8.750
8.056 .
8,810
10.000
10.000
9,022
9.000
8.083
8.889
9.000
6.667
9.583
7.692
9.286
8.750
8.238
9.375
8.667
7,796
9.167
7.4%
10.000
8.485
9,103
8,846
6,670
8.141
7.037
8.889
9,167

3.500
2,877
4.924
7.509
1,912
7,073
3.302
2,152
4,828
3,212
1.783
3.300
4,332
5,489
3.055
4,372
3.915
1,822
3.011
3.929
2,020
4.102
4,552
2,438
6.644
2,011
10,000
4.688
3,066
1.852
3,776
1.916
5.372
4,399
4.832
2,272
4.259
5.299
3.525
3.856
4.309
3.472
3.289
2.650
2,413
1.959
5,433
2,513
1.933

-----

%

57
88
94
85
88
97
83
59
76
95
90
66
95
71
95
95
76
89
58
89
91
91
90

2.a~

2,225
3.939
4,204
5,337
4.W
1,762
4.5211
3.122
2,544
4.078

clevelandfed.org/research/workpaper/index.cfm

Tabk 3. Concentration Statistics for Airports in Large Metropolitan Areas, 1989, continued

AirPo-

Suvcd by
All Airlines

Hcrfindahl Index
(overall service)
-

Metropolitan Area
111

\

-

Melbourne-Tiblsvill~PhBay. FL MSA
Memphis. TN-AR-MS MSA
Miami-Fort Lauderdale, FL CMSA (Fort Laudcrdale)
Miami-Fort Lauderdale, FL CMSA (Miami International)
MilwaukccRacine. WI CMSA
Minneapolis-St Paul. MN-WI MSA
Mobile, AL MSA
Nashv~lle.TN MSA
New Orleans, LA MSA
New York-N. NJ-Long Island, NY-NJ-CT CMSA (IFK)
New York-N. NJ-Long Island, NY-NJ-CT m S A (L~Guardia)
New York-N. NJ-Long Island, NY-NJ-CT CMSA (Long Island)
New York-N. NJ-Long Island, NY-NJ-CT CMSA (New&)
Oklahoma City. OK MSA
Omaha,NE-IA MSA
Orlando, FL MSA
Pensacola. FL MSA
Phladelphra-W1Imington-Tru1ton,
PA-NJ-DEMD CMSA
Phoenix. AZ MSA
Plusburgh-Beaver Valley. PA CMSA
Portland-Vancouver,OR-WA CMSA
ProvidenccPawtucket-Woomke&RI MSA
Raleigh-Durham, NC MSA
bchmond-Petenburg. VA MSA
Roanoke, VA USA
Rochester, NY MSA
Rock Island, lL MSA
Sacramento, CA MSA
Salt Lake City-Ogden, UT MSA
San Antonio. TX MSA
S n Diego, CA MSA
San Francisco-OaklandSanJose, CA CMSA (Oakland)
San Franasfo-Oakland-San Jose. CA CMSA (San Fmcim)
Sari Francisco-OaklandSanJose. CA CMSA (San Jose)
Santa Barbara-Santa Maria-Lompoc, CA MSA
S m t a , FL MSA
Savannah. GA MSA
Seattle-Tacoma, WA CMSA
Shreveporf LA MSA
South Bend-Mishawaka. IN MSA
Spokane,WA MSA
S t Louis, MO-lL MSA
Syracuse. NY MSA
Tampa-& Petenburg-Clcarwatcr. FL MSA (St Petusburg)
Tampa-St Pctcnburg-Clcarwater, FL MSA (Tampa)
Toledo. OH MSA
Tucson. AZ MSA
Tulsa, OK MSA
Washing(oq DC-MD-VA MSA (Nstioaal)
Washington, DC-MD-VA MSA (Dullu)
West Palm Beach-BocaRaton-Delray Beach,FL MSA
Wichita, KS MSA
Mean
Standard Deviation
Coefficient of Variation
Source: Variour airline service guldes, summr 1989, and autbors' ulculatioah

- -

-

Nonstop
141

Orre-*p

Nonstop
161

1.852
6,206
1.689
1 m
2628
5.184
2.099
4.186
1.358
28-47
1.460
4,200
2,710
1,690
1.327
1,552
2593
3,217
1.918
6.778
1,717
1.953
5,233
3.010
3,400
3,950

1.804
1.510
1.152
1.099
1.203
1.120
2.097
1,379
1,139
1.565
1.159
3,156
1,091
1.415
1,264
1.088
2089
1,096
937
1,217
1.439
1,569
1.734
2,171
2,695
1.793

8,056
9,259
7,300
7,848
8,636
8.469
9.375
8,674
9,111
8,034
7.849
10,000
7,500
8,667
9,615
7.244
9.375
8.438
7,280
9.010
7,528
8.333
8,690
8.462
10,000
9,118
9.286
7,639
8.714
7.917
7,427
7.255
6.498
6.583
8,333
8,393
8,750
7,125
9.375
9,500

--

On~stop
17l.

1x1 - --

-.

4,444
2677
2,189
2.027
2,604
2286
4,502
2.417
2.084
3.078
2,060
5.643
1.903
3.129
2876
1.892
4,313
1.968
1,807
2446
3.181
3.788
2.865
4.212
4.631
3,843
3.595
3,855
3.246
2,558
2,350
5,016
1,831
3,422
6,212
2873
4.480
1.803
5.000
3.729

clevelandfed.org/research/workpaper/index.cfm

Table 4. Vuiable D81nitionsand Data Sourca

Vuiable Nune

Definition

Data Source

HUB

Equalto 1 ifairportha
a hub &a (see table 2);
zero othenvise

Authors' ulculations

SERVICE

N u m b of airports in
sample reachable by nonstop
airse~iceFmmrirportin
1989

Airline flight scbcdules

INCOME

1987 per crpita p a s o d
inwme for M A cootlining
rirpofi

U.S. Department of Commerce.
county persod bmme
comp-1.pefle

POP

1987 population for M A
wnaining airport

U.S. Department of Commera.
county personal bmme
comp-wfile

COW

N u m b of Standard &
Poor's 500 companies
headquar(ered in hBA
or CMSA containing airport

Standud & Poor's Register
of Corporations. Dktclors,
md Executives. Volume 1.
1989

Sum of air miles Frofn

U.S. Department of
Tmmporcatioq Air
M a Staristics. Origin
md Datirution City
Paii Summary

airport to each of other
airports in sample

Mun

StMdud
Deviation

hkimmn

k i m m

0.31

0.47

0.00

1.00

15,896.06

2,624,541.96

2,469.18

4,171,725.32

122,403.68

47.058.39

1987 total employment in
hotels md ofhalodging
places (SIC 70) for M A
containing airport

U.S. Deputment of Commerce.
m t y business paDtans
comp-*file

13.805.34

18.311.88

1987 total anploymmt iu
murancut md -tion
services (SIC 79) for
MSA containing lirport

U.S. Department of Commerce.
county business paotanr
computer crpe Ne

10.666.14

17.969.31

BUSlWlR

Business-touristrctivity
proxy: residual fmm
regression of log(E7WE79)
on log(P0P) and log(INC0ME)

Authors' calculations

0.00

0.41

SNOW

Avenge number of days
snowfall exceeded one iDch

Loul ClimatologicalData,
National Ocunic and
Atmospheric Administration

FOG

Average number of days
visibility WJS 1/4 mile
or less

LoulClirnatologiul Data,

GATEWAY

Equal to 1 if airport bas
service to Europe, Asia.
or South Pacific; zcro
otherwise

OTHER

Equal to 1 if mdropolitan

Natiod Ocunic md
Atmospheric Administration
Airline flight schedules

Authors'crlculatiom

uea hrs mother rirport;
zero otherwiw
MINOR

Equalto1 ifairportisnot
the meeopolitan u u ' s
major airport (see text for
details); zem othuwise

Authors' crlculations

SLOT

Equdtolifrirportis
subject to FAA l ~ d h r g&
takeoff raeictions: zM
othuwiw

FAA

'

clevelandfed.org/research/workpaper/index.cfm

Table 5. Regression Results

Variable

Logic
Hub Equation
Dep. Var: HUB

OLS,
Service Equation
Dep. Var: SERVICE

OLS,
Nonstop, Airport
Dep. Var: HO

Estimated
Wald
Coefficient Chi-square

Estimated
Coefficient T-Ratio

Estimated
Coefficient T-Ratio

0.61
0.70
0.01
-0.55
-0.41
-1.28
-0.13
0.29.
3.57
-1.83
0.56
-5.73

log(poP)
log(INC0ME)
log(CORP+ 1)
log(D)
OTHER
MINOR
SLOT
GATEWAY
SNOW/365
FOG/365
BUSTOUR
CONSTANT
N
-2 log L
R-Squared
Note:

5.97 ***
1.60
0.08
-2.23 **
-2.06 **
-5.20 ***
-0.45
1.79
1.45
-1.30
4.48 ***
-1.32

-0.01
-0.22
0.00
-0.85
-0.11
0.61
0.08
0.42
2.67
0.46
0.01
19.80

110
139.091

*, **, and *** denote 10,5, and 1 percent significance levels, respectively.

Source: Authors' calculations.

-0.08
-0.50
-0.05
-3.45 ***
-0.56
2.46 **
0.25
2.56 **
1.08
0.33
0.08
4.56 ***

OLS,
Nonstop, Route
Dep. Var: HHO
Estimated
Coefficient T-Ratio

-0.02
0.02
-0.01
-0.19
0.00
0.11
-0.05
-0.06
0.54
0.44
0.00
11.29

-0.93
0.22
-0.32
-3.33 **
0.10
1.98*
-0.69
-1.47
0.96
1.36
0.01
11.35 ***

OLS,
One Stop, Airport
Dep. Var: H1

OLS,
One Stop, Route
Dep. Var: HHl

Estimated
Coefficient T-Ratio

Estimated
Coefficient T-Ratio

-0.24
-0.31
-0.06
-0.07
0.18
1.06
0.30
0.13
-2.64
1.66
-0.18
14.44

-3.65 ***
-1.08
-0.93
-0.41
1.42
6.55 ***
1.51
1.17
-1.63
1.79 *
-2.14 **
5.05 ***

-0.28
-0.41
-0.02
0.24
0.16
0.98
0.22
0.01
-1.30
1.06
-0.25
12.95

-5.70 ***
-1.95
-0.32
2.04**
1.71
8.22 ***
1.54
0.11
-1.10
1.58
-4.16 ***
6.21 ***

clevelandfed.org/research/workpaper/index.cfm

Table 6. Actual and Predicted H u b Values

Metropolitan Area
Chicago-Gaty-Lake County IL-IN-WI CMSA (O'Hare)
St. Louis, MO-IL
New York-N. New Jersey-Long Island. NY-NJ-CT (Newark)
b e a p o l i s - S t . Paul, MN-WI
Madelphia-Wilminptm-Trenton. PA-NJ-DE-MD
Cmcinnati-Hamilton OH-KY-IN CMSA
Atlanta. GA
Detroit-Ann Arbor. MI CMSA
Denver-Boulder. CO CMSA
New York-N. New Jersey-Long Island, NY-NJ-(JT(JFK)
Dallas-Fort Worth, TX CMSA (International)
HoustonGalveston-Bmria, TX CMSA (Intercontinental)
Los Angeles-Anaheim-Riverside. CA CMSA (LA International)
Miami-Fort Lauderdale, FL CMSA (MiamiInternational)
Boston-Lawrence-Salem,MA-NH CMSA
Las Vegas, NV
New York-N. New Jersey-Long Island, NY-NJ-CT (La Guardia)
Washington. DC-MD-VA (Dulles)
Plusburgh-Beaver Valley. PA CMSA
New Orleans. LA
San Francisco-Oakland-SanJose. CA CMSA (San Francisco)
Orlando. FL
ChicagoGary-Lake County. IL-IN-WI CMSA (Midway)
Raleigh-Durham. NC
Portland-Vancouver.OR-WA CMSA
Kansas City, MO-KS
Louisville, KY-IN
Seanle-Tacoma, WA CMSA
Memphis, TN-AR-MS
Nashville, TN
Cleveland-Akron-Lorain,OH CMSA (Hopkins)
Houston-Galveston-Braria, TX CMSA (Hobby)
Columbus. OH
sari h l 0 ~ 0TX
.
Phoenix, AZ
Salt Lake City-Ogden, UT
New York-N. New Jersey-Long Island. NY-NJ-CT (Long Island)
Indianapolis, IN
Miami-Fort Lauderdale, FL CMSA (Fort Lauderdale)
Milwaukee-Racine,WI CMSA
Buffalo-Niagara Falls CMSA
Tulsa, OK
Baltimore. MD
Oklahoma City, OK
Hamsburg-Lebanon-Carlisle,PA
Charleston. SC
Birmingham. AL
Tampa-SLPetersburg-Clearwater,FL (Tampa)
El Paso. TX
Daytona Beach. FL
Dallas-Foxt Worth. TX CMSA (Love Field)
Dayton-Springf~eld,
OH
Knoxville. TN
(3harloneGastoNa-RockW, NC-SC
Washington. DC-MD-VA (National)
Los hgeles-Anaheim-Riverside. CA CMSA (Burbank)
Syracuse. NY

Hub

Predicted Value

1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
1
0
1
1
0
1
1
1.
1
1
1
0
1
1
1
1
1
0
0
1
1
0
1
0
0
0
0
1
0
0
0
0
0
1
0
1
1
0
1
1
0
0

0.998
0.995
0.992
0.992
0.991
0.990
0.990
0.988
0.985
0.984
0.980
0.975
0.969
0.950
0.91 1
0.852
0.842
0.834
0.824
0.769
0.730
0.684
0.656
0.602
0.600
0.586
0.547
0.544
0.537
0.536
0.527
0.489
0.453
0.425
0.365
0.355
0.352
0.340
0.327
0.313
0.308
0.288
0.278
0.265
0.255
0.248
0.241
0.226
0.224
0.207
0.197
0.193
0.179
0.176
0.176
0.168
0.151

,

-0

*

clevelandfed.org/research/workpaper/index.cfm

Table 6. Actual and Predicted Hub Value, continued

Meaopolitan Area
Jacksonmlle, FL

Los Angeles-Anaheim-Riverside.CA CMSA (Ontario)
Los Angeles-AMheim-Riverside, CA CMSA (John Wayne)
Cleveland-Akron-Lorain,OH CMSA (Akron-Canton)
Rochester, NY
Jackson. MS
GreemilleSpartanburg. SC
Los Angeles-Anahem-fiverslde, CA CMSA (Long Beach)
Omaha. NE-IA
Chat&anooga. TN-GA
Grand Rapids, M
San Diego, CA
Mobile. AL
Tucson. AZ
Toledo. OH
Shreveport, LA
LtUe Rock-No& Linle Rock, AR
Richmond-Petenburg, VA
Lexington-Fayeite. KY
Wichita. KS
Colorado Springs. CO
Greensboro-WinstonSalem-HighPoint. NC
Albuquerque. NM
Davenport-Rock Island-Moline. IA-IL
Austin. ?X
West Palm Beach-Boca Raton-Delray Beach, FL
Tarnpaat. Petenburg-Clearwater. FL (St. Pelersburg)
Des Moines. lA
Pensacolq FL
C o r p u s ~ ? X
Melbourne-Titusville-Palm Bay. FL
AlbanySchenectady-Troy,NY
Augusta, GASC
Fayetteville. NC
Baton Rouge. LA
Evansville, IN-KY
Roanoke. VA
Columbiq SC
Fort Wayne, IN
South Bend-Mishawaka. IN
Allentown-Bethlehem.PA-NJ
Fort Myers-Cape Coral, FL
Savannah. GA
Providence-Pawtucket-FallRiver, RI-MA CMSA
Madison. WI
San Francisco-OaLland-San Jose. CA CMSA (San Jose)
San Francisco-Oakland-SanJose, CA CMSA (Oakland)
W e s t o n . WV
Sacramento. CA
Sarasota. FL
Fresno. CA
Spokane. WA
Santa BarbamSanta Maria-Lompoc, CA

Source: Authors' calculations.

Hub

Predicted Value

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0.148
0.145
0.139
0.137
0.135
0.127
0.127
0.124
0.120
0.1 18
0.115
0.114
0.112
0.112
0.090
0.090
0.087
0.083
0.082
0.076
0.073
0.07 1
0.067
0.067
0.064
0.060
0.056
0.052
0.052
0.047
0.045
0.044
0.044
0.043
0.041
0.036
0.036
0.036
0.032
0.03 1
0.027
0. m
0.023
0.021
0.021
0.014
0.014
0.007
0.005
0.005
0.002
0.002
0.001

'

,