Well, think again... according to latest projections of the United Nations the major contributors to this growth would be Africa! Of course, to be taken with some buckets of salt (much can happen between now and then), but still an interesting view:
(from The Economist)
"ON MAY 3rd, the United Nations produced its two-yearly update of the world’s population, which includes projections. The numbers show small tweaks since 2008. The global population is likely to reach 7 billion in October 2011, not spring 2012. And it may still be rising in 2100 past 10 billion, rather than being flat by then. But the most dramatic changes are national, not global. America's population, now 310m, is likely to rise to 400m in 2050 and 478m in 2100. China's is forecast to fall by 400m between now and 2100. Russia’s population is now 142m; Afghanistan’s slightly more than a fifth of that; Niger’s barely a tenth. But by 2100, Afghanistan is forecast to have the same population as Russia (111m) and Niger will be larger. Such forecasts need to be taken with a bucketload of salt: tiny shifts in today’s birth rate extrapolated over 90 years produce huge changes. But the general picture is probably right. Sub-Saharan Africa’s current population, at 856m, is little more than Europe’s and a fifth of Asia’s. By 2050 it could be almost three times Europe’s and by 2100 might even be three-quarters of the size of Asia. By any measure, Africa is by far the fastest-growing continent."