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Is Population Growth Bad? Economic
growth and population growth, two papers. There are still four
very common issues with empirical studies that attempt to link
population growth with economic growth.
One, many still use GDP (or GNP) per capita.
At its root all this research says is that three year olds work less
than thirty year olds so if rapid population growth is associated
with changes in the age composition of the population it will be
associated with changes in output per person because the
number of people of working age will vary. This is obvious
empirically, but not so obvious why anyone cares as the welfare
of each person might be unchanged. That is, imagine each
person has the same lifetime utility as the labor-leisure choice is
welfare maximizing--then GDP per capita goes up and down with
cohorts but welfare is the same all the time.
Second, there is very little decomposition
into causes of the effects on growth--as at least according to the
"received theories" population should affect growth through
accumulation and not though TFP.
Third, there is very little distinction between
whether having a large population is bad or whether having a rapid
change in the population is bad. It is perfectly plausible
that a country is both underpopulated and population
growth is too rapid.
Fourth, for the above reason and others, almost
certainly the effect of population growth should be interactive--one
would not expect the same effect of a 2 percent per year population
growth in every circumstance.
Here are two papers that address at least some of those problems.
Where in the World Is Population Growth Bad?
(with
Jeff Kling). 1994. This paper attempts to look for
interactive effects in the relationship between growth of GDP per
worker and labor force growth. It looks to stratify countries
into land abundant and land scarce countries, and other plausible
classifications. But none of the interactive terms works as
expected, leaving the mystery as deep as ever (I don't believe
subsequent work has done much to resolve this issue, reverting to
imposing equal effects across countries).
Population Growth, Factor Accumulation and Productivity
(1996). This paper decomposes the effect of population growth
into a labor force as a fraction of population, capital stock per
worker, human capital (years of schooling) per worker, and the
residual (called TFP). None of the channels works as expected
as population growth is not strongly related to per worker
accumulation of either physical or human capital.
Demography and Savings: What is to be done?
These were comments at a conference in 1997 on the then new
"demographic bonus" literature that related savings and
demographics. I tried to thrash the life out of this
"demographic bogus"--but did not drive the stake deep enough as it
went on to enjoy great fame. This is one of my favorite papers
as it includes a picture of my family as an argument against too
facile an association of "income per capita" and
"well-being"--mainly by pointing out how cute my third son was (and
is).
Concerns about
population growth go beyond economic growth to sustainability.
I suspect these concerns are more valid as externalities can easily
be exacerbated by larger populations. Two papers examine the
connections between population and local environment
(particularly water and firewood) looking for a environmental
"vicious circle" in which deterioration in the physical environment
raises the private demand for children because they are specialized
in local environmental good "collection" tasks (e.g. firewood,
water, fodder/grazing).
Environmental Degradation and the Demand for Children: Searching for
the Vicious Circle (with Deon Filmer).
Environment and Development Economics
7:123-146, 2002. (pre-publication
paper
and tables and
figures). This paper examines a data set with detailed
information on female time use and firewood collection in Pakistan
to examine the links in the vicious circle story.
Environmental Scarcity, Resource Collection, and the Demand for
Children in Nepal (with
David Loughran). 1997. This paper examines the same set of
issues of local environmental scarcity and fertility behavior in
Nepal. It provides a look at scarcity, productivity, and fertility
behavior.
How can many (or few) people support the earth?
This is a presentation at the Smithsonian Institution, a
counter-part to Joel Cohen's that makes the point that the answer to
"how many people can the Earth support?" depends entirely on how the
people treat the earth's resources, which in turn depends on
economic incentives and property rights. This uses the
example of a district in Kenya that had soil erosion problems in the
1930s--and has much less erosion problem now with five times more
population as there are incentives to invest in the land. Also
a
review of his book.
Fertility
and the Environment. A conference presentation that
reviews the linkages between fertility and "the
environment"--distinguishing amongst the various types of
"environmental" issues by their market failure characteristics--e.g.
between resources, ambient pollution, etc.
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