World population was transformed in the 20th century as technological and social changes brought steep declines in birth and death rates. The century began with 1.6 billion and ended with 6.1 billion mainly because of unprecedented growth after 1960. The momentum created by this may carry the world well past 7 million by 2015. It is certain that nearly all future population growth will occur in the developing regions, especially urban areas.
The percentage decadal growth during 2001-2011 has registered the sharpest decline since Independence. For 2001-2011 this decadal growth has become 17.64 per cent, a decrease of 3.9 percentage points from the 21.54 per cent for the period 1991-2001. Uttar Pradesh continues to be the most populous state of the nation with almost 200 million followed by Maharashtra, Bihar, West Bengal and Andhra Pradesh.