Sunday, November 20, 2005

Population Growth still seen as a Liability

Tyler Cowen recommended an interview at the Richmond Fed of Robert Moffitt, a labor economist from Johns Hopkins. Most of the interview was about the surprisingly good (but unheralded) outcomes from welfare reform. Most of the interview was about the surprisingly good (but unheralded) outcomes from welfare reform. I was surprised to see Moffitt claim that the mainstream view (represented by the NAS) has moved to agreement with Julian Simon that population growth is actually beneficial in most cases:

RF: There are some who have argued that population growth will ultimately lead to severe social and economic problems. I'm thinking of people like Paul Ehrlich, for instance. And then there are others — Julian Simon probably being the most prominent example — who have argued that population growth has unambiguously positive effects. Let us assume that these two positions define the extreme positions of the debate. Which one do you find more consistent with the evidence?
Moffitt: Although I have done work on the economics of fertility, I have not done work on this specific question. However, I have followed the debate fairly closely. As far as I can tell, the best work on that issue can be found in a couple of volumes put out by the National Academy of Sciences that examined how population growth affects a whole host of issues, including the environment, health, per-capita income, and others. And when you look at the data, it's fairly hard to find major negative consequences of population growth. You can build models where this might be the case, but the empirical evidence seems fairly straightforward, and it is closer to Julian Simon's view than to Paul Ehrlich's.
I think that economists have generally been persuaded that population growth, on average, has positive effects — and so, too, have demographers, a group that used to include a pretty large number of population growth opponents. Also, I think most people would agree that we do not face a "population bomb" except, possibly, in Africa, and AIDS has changed things rather dramatically there. Quite the opposite: In many developed countries, population growth is now below the replacement rate.

So I went off to find the NAS studies Moffitt referred to. I was disappointed to find mostly articles reiterating scientists' concerns about the effects of population growth. Joint Statement by fifty-eight of the World's Scientific Academies:

Representatives of national academies of science from throughout the world met in New Delhi, India, from October 24-27, 1993, in a "Science Summit" on World Population. The conference grew out of two earlier meetings, one of the Royal Society of London and the United States National Academy of Sciences, and the other and international conference organized by the Royal Swedish Academy of Sciences. Statements published by both groups expressed a sense of urgent concern about the expansion of the world's population and concluded that if current predictions of population growth prove accurate and patterns of human activity of the planet remain unchanged, science and technology may not be able to prevent irreversible degradation of the natural environment and continued poverty for much of the world.

And later: The Earth Is Finite

The growth of population over the last half century was for a time matched by similar world-wide increases in utilizable resources. However, in the last decade food production from both land and sea has declined relative population growth. The area of agricultural land has shrunk, both through soil erosion and reduced possibilities of irrigation. The availability of water is already a constraint in some countries. These are warnings that the earth is finite, and that natural systems are being pushed ever closer to their limits.

The first pages of Google hits include a couple of copies of a 1997 Joint Statement by NAS and the Royal Society of London whose first paragraph ends with this:

It has often been assumed that population growth is the dominant problem we face. But what matters is not only the present and future number of people in the world, but also how poor or affluent they are, how much natural resource they utilize, and how much pollution and waste they generate. We must tackle population and consumption together.

Summary: Without evidence, many believe that population growth is a problem, but it's not the biggest part of the problem. Population growth remains a problem to be addressed.

The National Academies Press ties teaching about Population Growth to evolution (which it is trying to teach in a science based way). The main messages concern limits to growth and carrying capacity. Population growth is exponential. Living organisms have the capacity to produce populations of arbitrarily large size, but environments and resources are finite. No mention of the effects of increasing population on standards of living or development of new technology.

Sigma Xi (The Scientific Research Society) 1991: This forum concluded that global trends in population growth and environmental degradation are on an unsustainable course, but it's not too late to change direction.

Admittedly most of these references are 5-10 years old, but google couldn't find anything more recent, even when directed to the NAS site. Bottom line: I couldn't find any evidence to support Moffitt's claim. I'm disappointed, but not surprised.

No comments: