Don, we're not talking about delaying childbirth from 25 to 45 years. It's more on the order of delaying from 18 to 25 or in some countries from 12 to 20.
The chance of birth defects certainly does go up with age although not as high as you have been told.
Tez, the distribution is interesting. A lot of Asia went through the D.T. in our lifetime. The countries that are still in the high-birth, low-death section are largely in Africa and Latin America. The real anomalies are almost all resource-rich Muslim countries. They lowered the death rate, but female emancipation and economic power has been suppressed. And they haven't really developed modern economies, so female participation in the paid workforce still lags.
MBuzzy, the Tragedy of the Commons is not nearly as true as its authors and supporters would like you to believe. Their research - and I use the word very loosely - was quite tendentious. They were tying to prove that common-property resources just wouldn't work and that radical privatization was the only solution.
Fortunately, it doesn't really work that way.
Consider the original commons in England before the Enclosure Acts. The contention was that everyone would have an incentive to put extra sheep on the common land giving himself more sheep at the cost of degrading the pasture. Of course, a single owner - the local Lord - would behave efficiently. So it was only right for him to take over the commons.
In fact, it turned out that stockmen had a very good idea of how many sheep could be raised on a plot. And later research shows that the people who used the land implemented very effective methods to make sure people were well-behaved. The local Lord was actually less efficient about raising sheep and generally turned farmers into tenants, threw them off the land to starve or engaged in rent-seeking behavior (economic-speak for "I have a monopoly and will put the screws to you) with no regard to actual productivity. His job was land owner, not sheep raiser.
The same theory has been applied to everything water to clean air to plant varieties to the genes in your own personal cells. The record for radical privatization has been pretty dismal. Oh, it's made a lot of money for a few people. But a very good case could be - and has - been made that the value thus added has been more than outstripped by the increase in transaction costs, the effect of rent-seeking and increased barriers to entry reducing competition.
