It is impossible to project 50 years into the future and accurately predict what the world population will be, it could less than double, just as likely as more than double, and the difference could be more than a billion. The number and size of the variables is astounding when trying to calculate future population. It has been shown that as people rise above poverty level their population growth lowers, (the rich have fewer babies than the poor). So if we continue to feed the poor they will continue to have more than one child per adult, but if we teach them capitalism they will feed themselves generate personal wealth and begin to feed others as well. Then they will be producing more than they consume and they will be too busy and too educated to contribute to a population explosion. On the other hand Islam may succeed in stopping the spread of capitalism and the world would be awash with men with several wives and dozens of children. The only way to feed the world is to teach the world to work together through capitalism and free trade.