REPLY Limits to Growth Plan B (SD7056)

[SDMAIL Bob Eberlein]

Posted by  Bob Eberlein <bob at vensim.com>

The obvious answer to Khalid's post is that the positive connections 
from economic prosperity to population growth work through mortality and 
not fertility. Better economic conditions lead to longer lives, hence 
more people. This, unfortunately, does not lend itself to any obvious 
meaningful policy changes. There is some evidence, and certainly an old 
standing belief, that economic prosperity does lead to decreases in 
fertility and there may be ways to strengthen that connection.

Ray's post, however, triggered an interesting thought for me. The old
demographic view of the world I allude to above is that people have 
large families to  accommodate high infant mortality, and to provide 
support in the parent's old age. However, in many places - for example 
Kuwait - that view does not apply. In this case there is, relatively 
speaking, prosperity that is being diluted by high population growth.

The oil rich countries may be extreme examples, but the old idea that a
country transitions from high fertility, high mortality to low
fertility, low mortality has been extremely confused by the importance
of external influence. Most specifically, the ability to effectively
target certain sources of mortality means that countries end up with
people living longer than they might otherwise expect given overall
social and economic conditions.

It is very interesting to look at a graph of population for Zambia
which, as Ray has pointed out, probably has growth beyond its own
ability to employ people. Zambia is a country ravaged by AIDS and it
appears that fertility has made a response to that threat. Though there
was an actual decrease in population a decade ago the current growth
rate appears to have increased. Populations can, it seems, respond
fairly quickly to bad news about mortality, but it is not clear that the
opposite is true.

         Bob Eberlein
Posted by  Bob Eberlein <bob at vensim.com>
posting date  Mon, 26 May 2008 06:00:43 -0400