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VOL. 7, NO. 2
FEBRUARY 2012­­

EconomicLetter
Insights from the

FEDERAL RESERVE BANK OF DALL AS

Global Stock Market Linkages Reduce
Potential for Diversification
by Karen K. Lewis

Comovement across
international financial
markets highlights U.S.
equity markets’ exposure
to foreign markets.

R

ecent European government debt difficulties demonstrate how
linked stock markets have become. Problems in countries such
as Greece and Italy have depressed stock markets not only on the continent
but also in the United States. Such comovement across international financial markets highlights U.S. equity markets’ exposure to foreign markets.
The apparent riskiness of this international exposure sharply contrasts
with a long-standing view that exposure to foreign stock markets helps reduce portfolio volatility for American investors. This perspective holds that
U.S. investors’ holdings of domestic assets such as stocks and bonds should
be augmented by securities in foreign markets because the two regions do
not move in lockstep. When the U.S. market decreases, foreign markets
may decline by a lesser amount or may even grow, thereby reducing risk.
But procuring foreign securities may be difficult, often involving a
foreign broker and the institutional red tape of an unfamiliar market.
Moreover, the accounting standards and legal conventions can be quite
different from those in the U.S. While in principle foreign stocks can help
diversify U.S. portfolios, information costs can more than offset those gains.
Putting these concerns together with the recent high correlations
across stock markets prompts questions about foreign holdings. Is it still
true that foreign stock markets provide diversification benefits to domestic investors? If so, might foreign stocks traded in the U.S. provide those
benefits without the need to go abroad? And how do we understand these
relationships in light of recent events in the global stock markets?
Arguing for International Diversification
The argument for foreign diversification is similar to the one for
holding both bonds and stocks in a portfolio: Domestic and foreign

Chart 1

Foreign Portfolios Offer Risk-Return Trade-Off
Average annual return (percent)
12.8
12.6
100%
foreign

12.4
12.2
12.0
20%
foreign

11.8
11.6

Minimum variance

100% U.S.

11.4
14

16

18
Average annual variance (percent)

20

22

SOURCE: Thomson Reuters.

securities do not move one-for-one.
Therefore, holding foreign stocks
alongside domestic U.S. stocks can
reduce volatility relative to a portfolio
of the U.S. market alone.
The U.S. market—as measured by
the Standard & Poor’s 500 Index—and
the foreign market—tracked through
the Europe, Australasia and Far East
(EAFE) Index, a broad collection of
non-U.S. firms—are shown in Chart 1.
Using data spanning the past few
decades, the chart shows the average
annual mean return and variance—a
measure of volatility—of different portfolios of U.S. and foreign indexes. The
point labeled “100% U.S.” shows the
mean return and volatility if an investor had held a portfolio entirely in the
S&P 500. By contrast, the point labeled
“100% foreign” shows the mean return
and volatility if an investor had placed
a portfolio completely in the EAFE.
Clearly, these two points highlight the
general perception that foreign returns
are riskier; the foreign portfolio leads
to annualized volatility about 6 percent
greater than the U.S. portfolio alone.
On the other hand, the entirely
U.S. portfolio does not generate the
least volatility. As the chart shows,

a portfolio with 20 percent foreign
stocks would have generated the lowest volatility and also a higher return
than the U.S. market alone.
Foreign Stocks Trading in the U.S.
Foreign diversification may be
achieved several ways. In a 1999
paper, Vihang Errunza, Ked Hogan
and Mao-Wei Hung challenged the
need to go to foreign markets to provide diversification.1 They showed that
portfolios of foreign stocks and multinational corporations trading on U.S.
markets such as the New York Stock
Exchange (NYSE) and Nasdaq can provide the same volatility reduction as
direct investments in foreign markets.
This can be achieved by buying
foreign stocks traded on U.S. exchanges typically in the form of “American
depositary receipts” (ADRs). These represent underlying shares in the company’s home market that are held by U.S.
custodian banks. While some ADRs are
traded in an over-the-counter market
among brokers, these stocks tend to
be of small market values compared
with those available on U.S. exchanges. Moreover, foreign companies listing
their stocks on U.S. exchanges must

EconomicLetter 2

F EDERA L RE SERVE BANK OF DALL AS

produce accounting statements meeting U.S. standards, thereby making
company information more transparent to Americans. Thus, much of the
attention for foreign diversification has
focused on the exchange-traded ADRs.
Over the past few decades, listing
stocks across international borders has
increased significantly (Chart 2). Until
the late 1980s, a negligible number
of companies listed their shares on
exchanges outside their home markets.
That began changing in the 1990s and
2000s, peaking just before the financial
crisis. The number of new listings has
remained near 2007 levels during the
past two years, retreating from highs
in 2008.
While these figures give a sense
of the increase in cross-border equity
listings, they do not indicate the shares
of foreign companies that U.S. investors could purchase in their home markets. At the end of 2011, there were
401 foreign companies trading as ADRs
on the NYSE and Nasdaq and another
four on the American Stock Exchange.2
A few of these have been in the U.S.
for many years. For example, Royal
Dutch Shell PLC of the Netherlands has
traded on the NYSE since the 1950s.
However, most companies entered the
U.S. market much later.
The proportion of foreign stocks
in each exchange by U.S. listing date
is shown in Chart 3, which is notable
for two features. First, the tenure of
companies on the exchanges mirrors
the general trend in Chart 2—most
companies came to be traded in the
U.S. market in the mid-1990s and later.
Second, the proportions of foreign
stocks listed in the 2000s experienced
sharp drops after the stock market
declines of 2001 and 2008.
Diversification Using Foreign Stocks
Even with U.S. investors’ increased
ability to diversify with foreign stocks,
how have these shares fared during
the recent financial events?
Because the benefits to diversification depend on how tightly foreign and
domestic stocks move together, we start

lowest variance in each year. In the
early 1970s through the 1990s, the
lowest volatility would generally have
been obtained with a relatively high
proportion of 50 percent or more in
foreign stocks. However, after the market decline in 2001, this relationship
changed sharply. To get the lowest
volatility in equity markets, the proportion in the foreign stocks would
be negative. That is, an American
investor would have to bet against the
foreign market by selling these securities, commonly called “short selling.”
Since short sales are difficult for small
investors, the lowest practical volatility
strategy would have been to hold no
foreign stocks.
The impact of these foreign stock
positions on reducing volatility relative
to the U.S. market alone is shown in
Chart 4B. With the exception of a few
years, such as 1983, diversification into
foreign cross-listed stocks would have
lowered volatility by 1–2 percent over
many years through 2001. After 2001,
American investors would have benefited from positions in foreign stocks
in the U.S. only if they could have bet
against them.

Chart 2

Foreign Stock Listings in Global Markets Trend Higher
Number of new global company listings
900
800
700
600
500
400
300
200
100
0

’85 ’86 ’87 ’88 ’89 ’90 ’91 ’92 ’93 ’94 ’95 ’96 ’97 ’98 ’99 ’00 ’01 ’02 ’03 ’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11

SOURCE: Citibank.

Chart 3

Proportion of Foreign Stocks Falls After Market Declines
U.S.-traded foreign stocks by listing date (percent)
15

10
NYSE (294 in 2011)
Nasdaq (107 in 2011)
5

0
’70

’72 ’74 ’76 ’78

’80 ’82 ’84

’86 ’88 ’90

’92 ’94 ’96 ’98

’00 ’02

’04 ’06 ’08

’10

SOURCE: Bank of New York Mellon.

by examining this comovement over
time.3 Interestingly, we find that foreign
stocks provide a better hedge against
the U.S. market before they begin
trading on U.S. exchanges. Once that
occurs, they move more closely with
the American market. This behavior
is consistent with the view that more
Americans hold these foreign stocks,

thereby inheriting similar risk factors.
We then study the behavior of an
index of these foreign stocks on the
NYSE and Nasdaq together with the
U.S. market index. We ask how much
risk within the U.S. portfolio could be
reduced by holding these foreign stocks.
Chart 4A shows the holdings for
foreign securities that would yield the

F EDERAL RESERVE BANK OF DALL AS

Lessons Learned
In general, foreign stocks should
provide diversification potential
because they are influenced more
strongly by events in their own markets. However, equity returns from
foreign companies listed on American
exchanges move much more closely
with U.S. market returns. As such,
they lose their diversification potential.
Moreover, when global markets are
affected by common sources of risk,
such as the European debt crisis, these
comovements are exacerbated. In
these times, the foreign diversification
potential is indeed diminishing.
Lewis is the Joseph and Ida Sondheim Professor
in International Economics and Finance at the
University of Pennsylvania’s Wharton School
and is a senior fellow in the Globalization and
Monetary Policy Institute at the Federal Reserve
Bank of Dallas.

3 EconomicLetter

EconomicLetter
Notes
1

companies, primarily due to the quantity of
Canadian stocks.

See “Can the Gains from International Diversi-

See “Are the Gains from Foreign Diversification

fication Be Achieved Without Trading Abroad?”

3

by Vihang Errunza, Ked Hogan and Mao-Wei

Diminishing? Assessing the Impact with Cross-

Hung, Journal of Finance, 1999, vol. 54, no. 6,

Listed Stocks,” by Choong Tze Chua, Sandy Lai

pp. 2075–2107.

and Karen K. Lewis, University of Pennsylvania,

2

Wharton School, Weiss Center for International

Companies from Canada and Israel may directly

list on these markets by agreement with the U.S.

Financial Research, Working Paper no. 10-1,

government. Including these companies would

February 2010.

significantly increase the total number of foreign

is published by the
Federal Reserve Bank of Dallas. The views expressed
are those of the authors and should not be attributed
to the Federal Reserve Bank of Dallas or the Federal
Reserve System.
Articles may be reprinted on the condition that
the source is credited and a copy is provided to the
Research Department of the Federal Reserve Bank of
Dallas.
Economic Letter is available free of charge by
writing the Public Affairs Department, Federal Reserve
Bank of Dallas, P.O. Box 655906, Dallas, TX 752655906; by fax at 214-922-5268; or by telephone at
214-922-5254. This publication is available on the
Dallas Fed website, www.dallasfed.org.

Chart 4

Ability of Foreign Stocks to Reduce Volatility Is Limited
After 2001
A. Portfolio Share of Foreign Stocks with Lowest Volatility
Index
1

.5

Richard W. Fisher
President and Chief Executive Officer

0

–.5

Helen E. Holcomb
First Vice President and Chief Operating Officer

–1

Harvey Rosenblum
Executive Vice President and Director of Research

–1.5
’73

’75

’77

’79

’81

’83

’85

’87

’89

’91

’93

’95

’97

’99

’01

’03

’05

’07

’09

Robert D. Hankins
Executive Vice President, Banking Supervision
Director of Research Publications
Mine Yücel

B. Volatility Increases After 2001

Executive Editor
Jim Dolmas

Percent
6

Editor
Michael Weiss

5

Associate Editor
Jennifer Afflerbach

4

3

Graphic Designer
Ellah Piña

2

1

0

’73

’75

’77

’79

’81

SOURCE: Thomson Reuters.

’83

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FEDERAL RESERVE BANK OF DALLAS
2200 N. PEARL ST.
DALLAS, TX 75201