Massimo Livi-Bacci has taken us on a fascinating tour of demographic history. What lessons for developments in the world today can we draw from the story he tells? I will distinguish between three types of lessons, which I call "economic lessons," "demographic lessons," and "cultural/political lessons."Demography ; Economic conditions

David N. Weil

English

Research Papers in Economics

DEMOGRAPHIC SHOCKS:T HE VIEW FROM
HISTORY. DISCUSSION
David N. Weil*
Massimo Livi-Bacci has taken us on a fascinating tour of demo-
graphic history. What lessons for developments in the world today can
we draw from the story he tells? I will distinguish between three types of
lessons, which I call “economic lessons,” “demographic lessons,” and
“cultural/political lessons.”
The economic lessons that we might look for would be answers to
questions like the following: What are the economic implications of the
demographic shocks that we are seeing? Will population aging, or slower
population growth, reduce output per capita?
The demographic lessons would provide us with help in forecasting
what exactly is going to happen on the demographic front. That is, what
will be the behavior of population in response to the kind of shocks that
we are seeing? Do we expect to see fertility rates in Europe rise back to
replacement levels? Do we expect to see a stabilization in population size
and/or age structure?
The cultural/political lessons would cover how countries respond to
these demographic shifts and to the large immigrant ﬂows that will likely
be occasioned by them.
ECONOMIC LESSONS
The facts of demographic change in the industrialized countries are
pretty well known, so I will mention just two. First, in coming decades,
population and labor force will be growing more slowly than at any time
in the last century; in many cases, populations will actually be shrinking.
*Professor of Economics, Brown University.For example, between 2000 and 2050, the populations in both Japan and
Italy are expected to shrink by 28 percent, if current fertility trends
continue. The economic consequences of low or negative population
growth per se are probably fairly minor. That is, it would not be hard to
imagine Italy ﬁfty years from now as a prosperous country that just
happened to have 28 percent fewer people. What makes low population
growth have a large economic impact is the second well-known fact: that
slow population growth is accompanied by a massive change in the age
structure of the population. In Italy, the median age of the population is
forecast to rise from 41 years to 53 between 2000 and 2050. In the OECD
as a whole, the fraction of the population ages 65 and over is forecast to
rise from 12 percent in 1990 to 17 percent in 2025.
Why is this rise in the fraction of the population that is elderly so
important? I want to argue that the simple answer to this question is not
the right one. The simple answer is that old people have to be supported,
and so more old people means a greater dependency burden. This simple
answer is wrong, for at least three reasons that I can think of. First, while
it is true that slower population growth means more old people, it also
means fewer children, who also place a dependency burden on society.
The total dependency rate—that is, the number of children and elderly,
divided by the number of working-age adults—will not be all that much
higher in the year 2030 than it was at the height of the baby boom in 1960.
The second reason that having a lot of elderly people is not necessarily a
problem in and of itself is that old people are increasingly healthy and
capable of working. Simply counting the number of people above a
certain age misses this phenomenon. Finally, the rise in the burden of
old-age dependency currently forecast has an effect on potential con-
sumption per capita that is small in relation to the effect of economic
growth. For example, in the United States, the expected rise in the fraction
of the population that is elderly over the period 2010 to 2030—that is,
when the baby boom retires—will have the effect of reducing potential
consumption by roughly 0.5 percent per year (Weil 1997). Given trend
consumption growth of roughly 2 percent per year, this effect of aging is
slightly unpleasant, but not terrible.
So a high percentage of the population being elderly is not, in and of
itself, a reason to predict economic catastrophe. What raises the danger of
economic catastrophe is the institutional context in which this aging is
taking place. Speciﬁcally, most old people in most industrial countries are
supported by the government. It does not have to be this way, of course.
Old people could be supported by their families, as are children; or they
could be supported by their own savings, as are the inhabitants of many
of the models that economists build. But at least for now, the fact is that
most elderly people are supported by public pension programs—and
given the ever larger fraction of the electorate that is elderly, it is likely to
stay that way.
DEMOGRAPHIC SHOCKS: THE VIEW FROM HISTORY: DISCUSSION 75These public pension programs pose two problems. The ﬁrst prob-
lem is that, in addition to supporting dependent elderly people, public
pension programs seem to do a remarkably effective job in inducing
perfectly healthy people to leave the labor force at ever younger ages,
which of course only worsens the ﬁscal problems associated with aging
(Gruber and Wise 1999). The second problem is that these public pension
programs are funded by distortionary taxation. As the programs get
bigger, the marginal distortion associated with every additional dollar of
beneﬁts grows. In the United States, where the population is still
growing, the Social Security system will be able to muddle through for
the foreseeable future with only minor tinkering. But in many other
countries, demographic change will rapidly push tax rates for existing
public pension systems to unsustainable levels. It is really the potential
burden of high tax rates to support government pension programs, rather
than the fact of aging per se, that constitutes the great danger of the
current demographic trends.
Unfortunately, history is not at all helpful to us in thinking about this
particular economic mess. Not only is the rise in the fraction of the
population that is elderly unprecedented, but retirement is also a histor-
ically new phenomenon, as is the massive transfer of resources to the
elderly through the channel of government. (For the case of the United
States, see Miron and Weil 1998.)
DEMOGRAPHIC LESSONS
The driving forces behind the demographic trends in the industrial
world are falling mortality, to a small extent, but mostly the dramatic
decline in fertility rates. In many rich countries, populations are not
coming close to reproducing themselves. In the United States, the total
fertility rate (TFR) in the year 2000 was 2.1 children per woman—that is,
exactly the rate that leads to a population reproducing itself. In France
and the United Kingdom, in the same year, the TFR was 1.7; in Germany
and Japan, 1.4; and in Italy 1.2 children per woman. Some of this
reduction in fertility rates is due to what demographers call the “tempo
effect”: If women in a country choose to delay childbearing, then a
temporary reduction in the fertility rate that we measure will follow, but
there will not be a long-term reduction in population growth rates. But in
many countries, the period of below-replacement fertility has lasted long
enough that it is now clear that more than the tempo effect is at work.
These fertility shifts are the underlying cause of the seismic shifts
that we are here to talk about. So what can demographic history tell us
about what to expect for the future? Speciﬁcally, does demographic
history give us any reason to believe that fertility in the industrial
countries will move back up to the replacement level?
The key point that I take away from Livi-Bacci’s work is that
76 David N. Weiltraditional demographic structures were homeostatic. That is, when they
were subject to shocks, they tended to rebound. If this same homeostatic
tendency is still present, then this seems like good news on the fertility
front. We can expect fertility rates to return to the level consistent with
population replacement. But before jumping to such a conclusion, we
should think about the source of the homeostatic tendencies in the
historical populations that Livi-Bacci has studied. Here I cannot help but
invoke the name of the patron saint of homeostatic population models—
and the most dismal economist of them all—Thomas Malthus.
Figure 1 is a simple representation of Malthus’s model. The upper
panel shows the relationship between income per capita and the size of
the population. For most of history, land was one of the most important
DEMOGRAPHIC SHOCKS: THE VIEW FROM HISTORY: DISCUSSION 77inputs into production, and a higher population meant a lower quantity
of land per capita, and lower income per capita. Thus, income per capita
is a negative function of the size of population. The lower panel shows the
relationship between population growth and income per capita. For most
of history, population growth has been a positive function of income per
capita. When there was enough to eat, population grew. In times of
scarcity, population shrank, either because of malnutrition or the delib-
erate suppression of fertility. The Malthusian model is, of course,
homeostatic. Population size will adjust until income is at the level
consistent with zero population growth.
Most of the demographic shocks that Livi-Bacci discusses in his
paper can be understood within this simple framework. Consider ﬁrst the
effect of a plague or war that wipes out a signiﬁcant fraction of the
population. A reduction in population will raise the level of income per
capita and temporarily raise the rate of population growth. Eventually,
the lost population will have been replaced, income will have fallen to its
pre-shock level, and the growth rate of population will return to zero. (In
Figure 2 this sequence of events is shown as a movement from point A to
point B and then back again to point A.)
The other shocks that Livi-Bacci discusses are those to productivity.
A great example of a productivity shock is the introduction of the potato
into Ireland in the eighteenth century. In our diagram, a positive
productivity shock of this sort is represented by a shift outward in the
curve relating income per capita to the size of the population. The initial
effect of the shock is to raise income per capita and the population growth
rate. Over time, higher population growth will raise the level of popula-
tion to the point where income per capita is once again consistent with
zero population growth. (In Figure 3, the initial increase in productivity
is represented by the movement from point A to point B, and the
subsequent rise in population is represented by the movement from point
B to point C.) In other words, the long-run result of higher productivity
will not be richer people, but rather more people at the same level of
income per capita.
Is this homeostatic process still operating today? We have little
reason to think that it is. First, the economic and demographic mecha-
nisms that underlay the Malthusian model have altered radically. Up
until the last century or so, higher incomes led to higher population
growth. In the industrial countries there now seems to be little relation
between population growth and the level of income per capita, while in
the developing world the Malthusian relation seems to have inverted, so
that higher income leads to lower population growth—as a famous
United Nations conference concluded, “Development is the best contra-
ceptive.” (Interestingly, in much of the former communist bloc we are
seeing that lower incomes also lead to a reduction in fertility.) Similarly,
the effect of population density on the level of income per capita, shown
78 David N. Weilin the top panel of the Malthusian diagram, has also gone away: Land is
now a relatively minor input into production, and countries that are
populous relative to their natural resources, such as Japan, can get along
quite well on imports.
The second reason that the lessons of the Malthusian regime are
probably not applicable today is that the nature of the shocks that
impinge on the population is so different. The historical sources of shocks
were plagues, wars, the discovery of new land, or improvements in
productivity like the arrival of the potato in Ireland. But the “shock” that
underlies the current seismic shift looks like none of these things. Rather,
it is a change in preferences: People simply want to have fewer children.
Why that is so is a fascinating question, but it is not one that is likely to
be answered by looking to history.
DEMOGRAPHIC SHOCKS: THE VIEW FROM HISTORY: DISCUSSION 79Once we are outside the Malthusian world, the homeostatic tenden-
cies that Livi-Bacci discusses are no longer present. There is nothing
natural about zero population growth, and, thus, no particular reason
why we should expect fertility in any country to be at or near the
replacement level.
CULTURAL/P OLITICAL LESSONS
Since I am even less qualiﬁed as a cultural or political analyst than I
am as a demographer, I will only sketch out why I think that the
cultural/political area is one where history may have some useful lessons
80 David N. Weilin thinking about current events. The issue on which I will focus is
immigration, in particular in the context of Western Europe.
Failing a dramatic restructuring of public pension programs and a
rise in the retirement age by something like a decade, the only way that
Western Europe is going to avoid a serious demographic/economic mess
is by becoming much more open to immigration. As I mentioned earlier,
the coming rise in the burden of old-age dependency was caused by a
dramatic fall in fertility. But this problem of aging cannot be ﬁxed by a
turnaround in fertility. The reason is simply that even if fertility did
suddenly rise, the new workers thus produced would not come on-
stream right away. Indeed, the immediate effect of a rise in fertility would
be to worsen dependency burdens for the next two or three decades.
The only potential source of needed workers is immigration. As
Livi-Bacci shows in his paper, both immigration and emigration have
played a stabilizing role in European history. France after World War I,
and all the Western European industrial countries after World War II,
made up for population losses with immigration; Ireland after the famine
of 1846 reduced excess population through emigration.
How much immigration would be required to prevent population
aging from leading to an economic disaster? According to a recent United
Nations report, the European Union will need 50 million to 75 million
immigrants over the next ﬁfty years. There is an ongoing debate about
whether Europe can cope with such a large ﬂow of migrants. The issues
are not economic, as far as I can tell, but rather cultural and political.
It seems as if this is a question that history may be some help in
answering. At a minimum, we can look to history to answer the question
of whether the proposed immigrant ﬂow is large in comparison to
available benchmarks. We can start by scaling the ﬂow against the current
population of roughly 370 million. Assuming that the immigrant ﬂow
keeps this ﬁgure from declining, a total ﬂow of 75 million immigrants will
average 0.4 percent per year. Is this a large number?
In the United States, over the period 1844 to 1910, annual immigra-
tion averaged 0.79 percent of the population, and in the peak decade 1900
to 1910, annual immigration was 1 percent of the population. Proposed
immigration into Europe equals only one-half of the U.S. benchmark. This
strikes me as an interesting ﬁnding. Obviously there are big differences
between historical ﬂows into the United States and current ﬂows into
Europe. For example, current immigrants are arriving into a well-
developed welfare state, whereas immigrants into the United States at the
turn of the century were pretty much on their own. And the United States
has always been culturally more tolerant of immigrants than has been
Europe. Nonetheless, this simple calculation suggests that the potential
shock of required immigration into Europe is not as large as is often
claimed.
DEMOGRAPHIC SHOCKS: THE VIEW FROM HISTORY: DISCUSSION 81References
Gruber, Jonathan and David A. Wise, eds. 1999. Social Security and Retirement Around the
World. Chicago: University of Chicago Press.
Miron, Jeffrey and David N. Weil. 1998. “The Genesis and Evolution of Social Security.” In
Michael Bordo, Claudia Goldin, and Eugene White, eds. The Deﬁning Moment: The Great
Depression and the American Economy in the Twentieth Century. Chicago: University of
Chicago Press.
Weil, David N. 1997. “The Economics of Population Aging.” In Mark Rosenzweig and Oded
Stark, eds., Handbook of Population and Family Economics. New York: North Holland.
82 David N. Weil

Demographic shocks: the view from history: discussion

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Demographic shocks: the view from history: discussion

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