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World Population Trends and Challenges
Lincoln University
Jefferson City, Missouri
October 4, 2004

F

or much of the last half century, public
discussion of population issues has
focused on the proposition that the
world faced a population explosion.
Many predicted dire consequences as population
growth rapidly used up supplies of exhaustible
resources such as metals and petroleum. The
standard of living would decline as certain essential resources became ever more scarce and costly.
This pessimistic view was not new. In 1798,
Thomas Malthus, in his famous “Essay on the
Principle of Population,” argued as follows:
The power of population is indefinitely
greater than the power in the earth to produce subsistence for man. Population, when
unchecked, increases in a geometrical ratio.
Subsistence increases only in an arithmetical
ratio. A slight acquaintance with numbers will
show the immensity of the first power in comparison of the second.

Thus, in Malthus’s view, population growth
will inevitably outstrip the earth’s capacity to
produce food, resulting in widespread famine,
disease, and poverty.
Modern concern over population growth
shares with Malthus the view that population
pressures will have dire consequences. However,
the Malthus view that these consequences are
inevitable—the view that earned economics the
label “dismal science”—is not shared by informed
observers today. For some, advocacy of rigorous
methods of population control has replaced
resigned pessimism. For others, a worldwide
decline in the birth rate seems to be solving the
problem without further government action.
If you ask people whether we must continue
to be concerned about a population explosion,

I’ll bet that nine out of ten will respond that the
problem will become extremely important in
coming years. Yet, experts who study these issues
say that the odds that population growth will
cause real difficulty in the foreseeable future have
receded. They emphasize instead that we face
another population problem that will be at hand
very soon—a rapidly aging population. Indeed,
we will soon face with certainty problems from
an aging population. Today’s college students,
early in their working careers, will be confronted
with this issue.
Because so few seem aware that the immediate
demographic problem is that of a graying population rather than an exploding one, I’ve chosen to
focus on aging in this lecture. However, I’ll begin
by discussing population projections to set the
stage for discussing issues raised by population
aging.
Before proceeding, I want to emphasize that
the views I express here are mine and do not
necessarily reflect official positions of the Federal
Reserve System. I thank my colleagues at the
Federal Reserve Bank of St. Louis for their comments, especially Dave Wheelock, assistant vice
president in the research division, who provided
extensive assistance. However, I retain full responsibility for errors.

WORLD POPULATION
PROJECTIONS
When Malthus wrote his treatise in 1798, the
world’s population totaled some 900 million
persons. Today, world population is roughly 6.4
billion persons, and about 100 million persons
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ECONOMIC GROWTH

are added to the total every year. Although we do
witness famine, disease, and poverty, as Malthus
predicted, these sad events are usually isolated
and reflect temporary problems, often created by
civil war. Across the world, food is generally more
abundant and less expensive, measured in terms
of the amount of labor that must be expended to
obtain a given level of nutrition, than it has ever
been. Agricultural productivity continues to rise
rapidly, and it seems unlikely that world food
supply will be a constraint on population growth
for years to come, if ever.
Still, in light of rapid growth of the world’s
population, especially over the last 50 years, many
people have questioned whether our current
population is sustainable. Echoing Malthus, some
commentators claim that the continuing population growth will create unsustainable pressures
on the world’s resources and raise pollution to
dangerous levels. Particularly prominent in recent
discussions is the threat of global warming from
emissions of greenhouse gases.
Let’s begin with recent projections of world
population growth from the United Nations. A
notable development is the changing distribution
of population between the so-called “developed”
and “less developed” nations. Population growth
has been much faster in the poorer countries than
in those with high standards of living and wealth.
Whereas the developed countries of Europe,
North America, Australia, and New Zealand
accounted for roughly one-third of world population in 1900, and about the same percentage in
1950, by 2000, those countries accounted for just
20 percent of world population. It seems likely,
however, that the population growth of many
lesser-developed countries will slow during the
present century, as I will discuss in the second
part of my talk.
World population has more than doubled in
the last 50 years, and has nearly quadrupled since
1900. Currently, world population is growing at
a rate of 1.35 percent per year. The United Nations’
most recent forecast, however, predicts a slowing
in the growth of world population to about 0.33
percent per year by 2050, at which time forecasters
2

are predicting that world population will total
8.9 billion persons.
Interestingly, by mid-century, U.N. forecasters
predict a world average fertility rate—that is, the
average number of children a woman will bear in
her lifetime—of 1.85. At that rate, fertility will be
below the level necessary for population to stay
constant—about 2.1 children per woman. Consequently, world population is expected to begin
declining sometime toward the end of this century.
Such projections must always be taken with
a grain of salt because they are based on a number
of assumptions that may not turn out to hold. In
the early 1930s, U.S. government forecasters
predicted that at the end of the 20th century our
nation’s population would total 145 to 150 million
persons. The forecasters didn’t count on the baby
boom that came along after World War II, however,
and their forecast turned out to be far too low. By
2000, U.S. population had reached nearly 300
million, or twice the level in the forecast made
70 years earlier.
I’ve already noted that population growth
during the last 50 years or so has been far higher
in relatively poor countries than in higher income
countries. Much of the increase in world population projected for the next 50 years is also forecast
to occur in lesser-developed countries (LDCs).
Whereas LDCs have a total population of 5.1 billion today, those countries are projected to have
7.7 billion persons and a population growth rate
of 0.40 percent in 2050. By contrast, many developed countries are projected to have falling populations by 2050.
On the surface, the disparate population
growth rates of the developed and developing
worlds may seem cause for alarm. Indeed, rapid
population growth, at least in the short run,
implies that poverty levels will rise unless supplies of food, shelter, and other scarce resources
increase as rapidly. In many developing countries,
employment growth lags the growth rate of the
working age population, leading to falling wages,
unrest, and emigration.
However, if we look at the reasons for the
disparate growth rates of population between
the developed and developing world in the 20th

World Population Trends and Challenges

century, there are reasons to be more optimistic
about the future. For centuries, the world’s population grew slowly, as high rates of mortality
largely offset high birth rates. Wars, famines, and
epidemic diseases caused many people to die
young, and average life expectancy was consequently low. In Europe, conditions began to
improve by the 17th and 18th centuries, with
increased food supplies and improvements in
personal hygiene and public sanitation. By the
19th and early 20th centuries, most European
and North American countries had experienced
a “demographic transition” from high rates of
fertility and mortality to low rates.
In most countries, the demographic transition
is seen first in a declining mortality rate. Because
the birth rate initially remains high, population
growth increases sharply. As the transition proceeds, however, the birth rate declines to approximate the lower mortality rate. Population growth
then slows. Most economically developed countries have completed this transition, but LDCs
are at the intermediate stage of low mortality, but
still high fertility rates. Consequently, their population growth is rapid.
The data indicate, however, that fertility rates
have declined substantially during the last 20 to
30 years in many LDCs. From 1970 to 2000, the
median fertility rate among LDCs declined from
5.9 children per woman to 3.9 children per
woman. If these trends continue, then population
growth will slow. If fertility rates do not change
from current levels, however, the U.N. projects
that the world’s population will be 12.8 billion
persons in 2050, instead of the 8.9 billion it forecasts as most likely.
Indeed, the U.N. projects that the average fertility rate among LDCs will fall below the replacement rate by 2050. Thus, toward the end of the
century, population in those countries is likely
to begin to decline. Some 20 nations classified as
lesser developed already have fertility rates below
replacement level, as do some 39 other nations.
Several LDCs continue to have high fertility rates,
however, and these include many of the world’s
poorest nations.
Fertility rates have also declined in many
developed countries, including some where fer-

tility rates were already low in 1970. In 2000, only
four developed countries—Albania, Iceland,
New Zealand, and the United States—reported
fertility rates at or above 2 children per woman.
With the exception of the United States, these are
all small countries.
The fertility rate is below 2 in most developed
countries, and in many cases substantially below.
Some representative examples are the United
Kingdom, 1.6, Germany, 1.4, Italy, 1.2, and Japan
1.3. The fertility rate in the United States is 2.1.
The United Nations attributes the substantial
decline in fertility throughout most of the world
to increased use of contraception, especially in
LDCs, and to an increase in the average age at
which women bear their first child, which has
been more pronounced in developed countries.
By the 1990s, the median age at first birth was
26.4 years in developed countries and 22.1 years
in developing countries.

A GRAYING POPULATION
A decline in the birth rate obviously means
that population growth will slow. But no fancy
calculations are required to understand that a
sharp decline in the birth rate will also create an
imbalance in a population; the decline in the
number of young people inevitably means that
the proportion of older people in the population
will rise.
While the world’s population growth has
slowed, there has, therefore, also been an aging
of the population. A good summary measure of
a population’s age is the median age—the age
such that half the population is older and half is
younger. Over the last half century, the median
age of the world’s population has increased by
2.8 years, from 23.6 in 1950 to 26.4 in 2000. The
U.N. forecasts median age to rise to 36.8 years in
2050. More-developed countries are expected to
have an increase in median age from 37.3 years
to 45.2 years, and lesser developed countries
from 24.1 years to 35.7 years. Japan is today the
country with the oldest population, having a
median age of 41.3 years. Japan is projected to
3

ECONOMIC GROWTH

have a median age of 53.2 years in 2050. The
median age of the U.S. population, by contrast,
is currently 35.2 years, and is forecast to be 39.7
years in 2050.
The world’s fastest growing age group is comprised of those persons 80 years and older. In
2000, 69 million persons, or 1.1 percent of world
population, were aged 80 or older. By 2050, the
number aged 80 or older is expected to more than
quintuple to 377 million and be 4.2 percent of
world population. In that year, 21 countries or
areas are projected to have at least 10 percent of
their population aged 80 or over. Indeed, Japan
is forecast to have almost 1 percent of its population comprised of persons aged 100 or more. The
United States is projected to have 7.2 percent of
its population made up of those 80 and older.
To understand the implications of the graying
population, think about a family living on the
U.S. frontier 150 years ago. The family was largely
self-sufficient, growing its own food, making its
own candles, and building its own house with
some assistance from neighbors. The working
members of the family had to grow the food for
the entire family, including children and elderly
grandparents. The children went to work at a
young age, and the grandparents worked in the
fields as long as they could. The larger the number of children too young to work and the larger
the number of disabled elderly, the greater the
burden on those in their prime working years.
The children and the elderly were dependents,
supported by those working.
The fact that we live in a high-income industrial society does not change the fact that those
working have to produce all the goods and services consumed by the entire population. Nonworking dependents are dependents just as surely
today as they were on the frontier 150 years ago.
Those of you soon to be in the working population will have to support yourselves and the
dependent population of children and elderly.
In frontier America, the elderly did not retire
to Florida on their Social Security and other pensions. They in fact worked as long as they were
able to work. They might not be able to do heavy
work in the fields but they could do less physi4

cally demanding work, and they did. The truly
dependent were those who were bedridden, and
with the medical technology available in those
days they usually did not live very long in such
a condition.
The United States and other high-income
countries have pension systems, such as our
Social Security system, to support the elderly.
But the Social Security system sets the retirement
date by the calendar and not by capacity to work.
Thus, today many and perhaps most retire while
physically able to work productively.
This “graying” of the population poses a
serious fiscal problem as the dependency ratio—
the ratio of persons out of the labor force to the
number of persons in the labor force—rises. Government pension systems—Social Security in
the United States—is where a rising dependency
ratio has its most obvious impact. Social Security,
like the public systems of most countries, is a
“pay-as-you go” system, meaning that today’s
benefit payments to retired persons are funded
by current taxes on working persons. Obviously,
as the number of those receiving benefits rises
relative to the number paying taxes, the average
taxpayer must shoulder a larger and larger burden
or, alternatively, benefits must be cut.
One way to think about Social Security taxes
today is that they are like the food grown by the
frontier farmer and his wife that they do not get
to consume because the food goes to their parents
and children—their dependents. Some of the
income earned by those working today has to be
diverted to provide benefits for retired dependents.
The burden will rise substantially in coming
years because the number of retirees will rise
relative to those at work.
There has been some careful work on this
subject by the Organisation for Economic Cooperation and Development (OECD), an organization comprised of economically advanced
democratic countries, including the United States.
OECD projections indicate that public transfers
to retired persons for pensions and health care
will increase in the average OECD country by 6
percent of GDP, from 21 percent to 27 percent,
between now and 2050. Unless promised future

World Population Trends and Challenges

benefits are cut significantly, substantial tax
increases will be necessary to effect such transfers.
However, as a recent OECD report concludes,
drastic tax increases could make matters worse
by reducing the incentives for market work and
for saving.1 Indeed, the OECD concludes that in
many countries it may be necessary both to reduce
promised benefits and to increase the incentives
for work.
In recent decades there has been a tendency
for people to enter the labor force at a higher age
while retiring at an earlier age. Consequently, the
proportion of life spent working has declined.
This phenomenon reflects a number of factors,
including increasing returns to education and
increasingly generous transfer programs that
encourage early retirement. In countries that
experienced a post-World War II baby boom, large
increases in the labor force in the 1960s and 1970s
reduced the dependency ratio and enabled
increasingly generous transfer payments to retired
persons. However, if life expectancy continues to
increase, as demographers project, the dependency ratio will rise and such transfers will constitute an increasing burden on those working.
It is worth emphasizing that as important as
it is to put the Social Security and Medicare trust
funds on a sound financial basis, doing so does
not necessarily solve the problem created by a
high dependency ratio. We can understand this
point easily by supposing that the Social Security
trust fund already held enough U.S. government
bonds to cover large benefit payments in coming
years. When the trust fund sold bonds to provide
funds to make benefit payments, who would buy
the bonds? The elderly wouldn’t be buying the
bonds—they are the ones who need the benefit
checks to pay for everyday living expenses. The
working generation would have to buy the bonds—
interest rates would have to be high enough to
persuade enough members of the working generation to buy bonds. Their purchases would provide the cash the Social Security System would
need to pay benefits to the retired generation. In
short, somebody has to give up consumption so
1

that those who are retired can have the consumption goods instead.
This discussion should make clear that the
fundamental problem our society—and all aging
societies—face is not fundamentally a financial
problem but instead a problem of an excessive
number of retired people relative to working
people. This is a problem we can solve, and it is
really a happy problem in many ways. We are
living longer and in much better health—that
can’t be a problem!
Nevertheless, an implication of living longer
should not be that younger people have to bear
the entire burden of providing goods retirees
will consume for those additional years. Would I
ask my own children, who have their own problems of supporting themselves and their families,
to support me so I can enjoy a life of retired leisure
of many years of travel and sailing, which are
two of my passions? I wouldn’t do that looking
my own children in the eye, and I don’t think we
as a society should collectively ask the younger
generation to support all the additional years of
retirement of the baby boom generation that
modern medicine makes possible.
Unless those in my generation and the babyboom generation want to place a huge burden on
our children and grandchildren, we need to adopt
some combination of the only two possible solutions. One is to reduce the annual payments to
Social Security beneficiaries, and the other is to
reduce the number of retirement years by raising
the retirement age. These changes—whatever
mix the country decides it prefers—should be
phased in gradually, to avoid an undue impact
on those who are close to retirement today. My
own preference is to concentrate on raising the
retirement age for full benefits, given that people
are healthy and productive much longer than
they used to be.
Rather than moving toward a later retirement
age, the public pension systems of many countries today actually encourage early retirement
by offering generous benefit payments to early
retirees. Although early retirees typically receive

OECD. “Strengthening Growth and Public Finances in an Era of Demographic Change.” May 2004.

5

ECONOMIC GROWTH

a smaller annual pension than persons who wait
until they are older to retire, the difference in
many countries is insufficient to discourage large
numbers of people from retiring early. The United
States is something of an exception. For a man
with average income, our Social Security System
is roughly neutral between ages 62 and 67. Beyond
that age, however, the incentive to remain in the
labor force is low. Put another way, the implicit
tax of remaining in the labor force—foregone
benefits—is relatively high. At a technical design
level, there are a number of possible ways to create a more neutral system with respect to retirement age, so that at a minimum those who want
to work longer are not penalized for doing so. The
idea is that annual benefits need to be higher by
an actuarially fair amount when retirement is
delayed.
A recent OECD study found a close correlation between incentives to retire and retirement
behavior—not surprisingly, people do respond
to incentives! The implication of this research,
according to its authors, is that labor force participation in the 55-to-64 age group would be
increased substantially by reforms that abolished
policy-induced incentives to retire early. Indeed,
the report goes on to suggest that policymakers
should consider skewing incentives against
retirement, at least up to some age, in recognition
that people who work provide a net positive
impact on public budgets.2 By continuing to work
past normal retirement age, people support themselves and pay taxes that help to reduce the tax
burden that would otherwise fall on others.
Several countries have begun to rein in their
public pension systems by instituting reforms
that reduce incentives to retire early or by raising
the age at which persons are eligible for benefits.
The United States, for example, has in place a
gradual increase in the retirement age for full
Social Security benefits from age 65 to age 67 by
2025. Our Social Security system was begun in
the 1930s when the average 65-year-old person
could expect to live about an additional 13 years;

2

6

by 2000, those additional years at age 65 had
risen to about 18. It makes sense that we lift the
age of eligibility for Social Security payments in
recognition of the increase in our expected life
spans. However, it is clear that the increase in
normal retirement age from 65 to 67 that is in
current law does not go far enough to solve the
problem.
The OECD has recommended a number of
other reforms to its member countries to encourage older persons to remain active participants
in the labor force. These include removing labor
market rigidities that discourage part-time employment and implementing reforms that would
increase the share of retirement income from private sources relative to public pay-as-you-go systems. Such policy reforms could help alleviate
the fiscal challenges posed by aging populations
both by lowering dependency ratios and by favoring economic growth.

CONCLUSION
Demographic change in the United States
and elsewhere in the world presents enormous
challenges. In much of the world, the combination of increased life expectancy and a reduced
birth rate has created a situation in which the
population is becoming unbalanced in its age
distribution. We know this problem is right ahead
of us, because the people have already been born.
I hope I have convinced you that Social Security
and Medicare are not just problems you will
have to deal with when you come close to retirement age, but problems you will have to address
within a few years. Taxes to support these retirement programs will fall on you, and not on those
already retired. Retirees will face the possibility
of benefit cuts, to be sure, but you will face the
problem of tax increases. We are truly all in this
situation together, and we had better find a way
to deal with it together.

This research is summarized in “Strengthening Growth and Public Finances in an Era of Demographic Change.” OECD, May 2004.