Posner‘s a nervous optimist:

But suppose world population will reach 10.1 billion by the end of
this century. Would that be a good or a bad thing? Arguably a good
thing, on several grounds. One is that it would enable greater
specialization, which reduces costs. Second is that it would increase
the returns to innovation by increasing the size of markets, though an
offset is that innovation can produce immensely destructive as well as
constructive technology. Third, the more people there will be, the more
high-IQ people there will be, and hence the faster the growth of
knowledge will be; though a possible offset is that the more evil
geniuses and other monsters there also will be; persons of great
potential for evil, such as Hitler, Stalin, and Mao, presumably are

The downside of population growth is the pressure it places on the
environment and natural resources, especially the former, since the
price system provides efficient rationing of resource use… Continued population
growth could combine with an acceleration of global warming to
precipitate a global catastrophe (perhaps a catastrophic water
shortage) within the next few decades, but 89 years from now the march
of technology may enable such problems to be solved. Think of the
technological advances of the last 89 years (that is, since 1922), and
imagine a comparable rate of technological advance applied to the
current level of technology, which is so much higher than that of 1922. 

But the beneficent effects of population growth, like the estimates
of that growth, are highly uncertain. The risk averse among us might
prefer a lower rate of population growth in order to reduce the
downside risks of that growth, even though the upside potential would
be reduced as well.

Becker‘s a calm optimist:

The substantial world growth in per capita incomes during the past
150 years has been associated with growing world populations. I believe
that declining populations are bad for long run economic welfare…

Given the sharp rise in food prices during this first decade of the 21st
century, it would appear difficult to feed adequately a much larger and
richer world population. Yet, unlike say the production of copper, no
natural limits sharply curtail the amounts of food that can be
produced. Food output will expand with a growth in the amount of land
devoted to food production-currently agriculture takes a small fraction
of the world’s arable land. Also, the world can invest much more in
fertilizers and in improving food technology, so that greater output
can be squeezed out of each acre used to grow corn, wheat, soy, dairy,
meats, and other foods.

Greater demand for water due to larger populations and greater
wealth would make clean water scarcer… [But] With
sensible prices, the available water should be sufficient to satisfy
all essential water needs of a much larger world population.


A larger population combined with growing per capita incomes would
increase global warming and worldwide pollution… [T]he world should be prepared to meet
various worst-case climate scenarios. This would require the
development of mitigation techniques that can be rather quickly ramped
up in case global warming turns out to be a severe problem… Such technologies are certainly achievable by the end of the
century with substantial private and public investments in developing
new methods to capture and store various harmful gases emitted by
fossil fuels.

If world population grew to 10 billion by the end of the century-an
unlikely outcome- that would present considerable challenges. However,
greater population would add real benefits as well, and I am inclined
toward the view that the benefits will exceed the harm.

Both more reasonable by far than Bad Religion’s “10 in 2010,” but the song’s too singable to hate.

* I make the same point at greater length here.