According to UN the world population reached seven billion on 31/10/2011. How correct is UN is a separate issue as there is no round-the-clock monitoring of population all over the world.
Population growth is slowing down and world population is expected to stabilize when it reaches nine billion. However floods, earthquakes, cyclones and other natural calamities play a part. In some countries there has been decline over the years and they want to increase their population. Russia, Australia, France, Germany, Ireland, Japan, South Korea and Singapore want more people.
There is enough food in the world for seven billion people and the world can have more food for more people. Starvation and malnutrition are not due to population growth but due to other reasons. Shelter will not be a problem as tall buildings can accommodate more people.
India is expected to overtake China by 2030. If China gives up one-child policy it can remain the most populous country. The policy has resulted in female infanticide. Many Chinese men will have no women to marry unless they resort to polyandry. Many women have got around the policy by using fertility drugs and having twins or more children at one time. In India there is no one child policy but there is female foeticide. Many Indian men will have a problem.
At one time Europe was populous with high population growth. Europeans went to America, Australia and Africa. Those who went to Asia were comparatively few. Now there is migration from Asia and Africa to Europe.