Earth's Population in the Xxith Century

What will happen in the XXI century? Will economic and social growth progress faster than population growth? Will it be proved that the world can sustain a bigger population than it is now? What is surely known is that basic information about the population will continue to be essential to understand the human behavior and to anticipate changes. It is certain that the start of the XXI century is under major human society changes identified by its evolution on economical or political aspects, but especially in terms of population (demographic resources).