The BRICS nations believe they are under represented in terms of voting power at both the IMF and the World Bank. They think the voting shares used at these international institutions are out of date and don't reflect the current strength of their economies. That is a debate that will probably only intensify in the future. But one thing we can all agree on is that a lot of people live in the BRICS nations (over 3 billion). Here is a map that shows that in an easy to visualize format based on current population.
(world map based on population instead of land mass)