Well seams like China will take a place as strongest economy in the world sooner. India will be just after China probably becouse both India and China are growing alot more and more.

World strongest Economies and population in 2010:

-The European Union: 19.920 trillion of US$ (Population: 857 million)
-United States: 14.660 trillion of US$ (Population: 305 million)
-Japan: 5.458 trillion of US$ (Population: 125 millon)
-China: 6.400 trillion of US$ (Population: 1.3 billion)

These 4 Countries has the strongest Economies in the world wich are going over 5.000 trillion of US$ (Sorry i know there are alot more rich countries but i just gave example about Countries that have more then 5k trillion US$).

Well here's about year 2020:

http://www.bionomicfuel.com/the-world-economy-in-2020-the-10-big-winners-and-losers-part-1/
http://www.bionomicfuel.com/the-world-economy-in-2020-the-10-big-winners-and-losers-part-2/

There was people counting on winter or around that time i think it was on this year winter , heard on news and ye , theres aroun 1.3b of them .