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In the area of population there are two big questions: what, if anything, is negatively affected by population growth? and If population growth is negative, what, if anything, can or should be done about it?
Swimming, Smoking, Solving. I was invited to a panel at the 2008 Population Association of America meetings about Matthew Connelly's book Fatal Misconception. This was my presentation, a brief history of the "family planning" movement.
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.
Desired Fertility and the Impact of Population Policies. Population and Development Review, Vol.20 (no.1), March 1994. This paper makes the very simple, but controversial, point that nearly all of the cross-national variation in the total fertility rate is associated with the reported desired fertility rate. The reduction in the gap between actual and desired fertility accounts for almost none of the "demographic" transitions--reductions in desired fertility are (nearly) all of the action. This suggests focusing on women's preferences for children and the conditions that cause those to change: increased prosperity, women's education, better health, women's empowerment are the key to the fertility transition with the supply of family planning services per se playing a small role.
(there were comments and replies on this paper in the next issue of the journal--which got quite nasty. I include my reply (they can include theirs on their web site).
One very popular concept among advocates of family planning is the "unmet need" for contraception. The following two papers attack this notion as neither analytically sound nor a sound basis for programs.
No Need for Unmet Need. (1996). This was a presentation at Johns Hopkins that argues the concept of unmet need is analytically unsound.
"Unmet need" Needs to Go. (2001). This was the reaction to the 2001 PDR piece by Casterline and Sinding attempting to revive the use of "unmet need." It argues that even for committed family planning advocates the concept is worse than useless.
Population and Copulation (1995). This was presented at the 1995 meetings of thePAA (Population Association of America). It argues that demographers had, by and large, ignored sexual activity in discussions of contraception. Once one acknowledges the close link between population and copulation it changes the view of the primary benefits of improved contraception from reduced unwanted fertility to more unrestricted sexual activity.
The "Lie of the Land"