[bdhe]

Its also interesting to note how much the demographics of the world has changed and will be changing over the next 40 yrs or so.

These are outdated links, but take note of the top 10 most populated countries in 2050. The fact that Nigeria, Ethiopia and DRC are projected to enter the top 10 list will lead to interesting consequences for Africa.

http://www.photius.com/rankings/world2050_rank.html

http://www.kulzick.com/pop100.htm

Also since independence in 1947, Pakistan's population has grown to 177 million today from around 30 million (a six-fold increase). And is estimated to end up at a whopping 270 million over the next couple of decades. Similarly, Nigeria is also witnessing a population explosion starting off with around 55 million in 1971 and right now at ~150 million.

Edit: The UN has a nice website where one can get much more detailed information about population projections.

http://esa.un.org/unpd/wpp/unpp/p2k0data.asp