The world's population, which is approaching 8 billion people, has become a troubling issue. The UN has launched a global initiative to tackle childbirth in 12 countries where child and adolescent marriage is prevalent.

In 1979, the country promoted "population control" through its birth control program and one-child policy. "China may fall economically if some miracle of productivity does not occur for it," says Charles Goodhart, co-author of the book "The Great Demographic Revolution" and professor at the Goodhart School of Economics.