According to the US Census Bureau, population on Earth is still growing at a heady pace -- 74 million more people were born than died in 2002 -- but the pace of growth is slowing. In 1990, the average woman gave birth to 3.3 children over her lifetime; by 2002, that rate had dropped to 2.6 children, slightly above replacement level. The Census Bureau believes that this rate will drop below replacement by 2050, at which point the planet will hold just over 9 billion people, 17% of which will be over 65.

Sadly, this is only partially due to women choosing to have fewer children; much of the decline comes from the effect of AIDS in Africa. But even if a freely-available cure were developed tomorrow, these projections wouldn't really change. Population is a slow-moving indicator, where results of even big changes can take years, even decades, to appear.