According to the United Nations, the world’s population reached seven billion in late 2011. For many, this landmark was seen as a clear sign of crisis: an indication that humans are reproducing unchecked, leading us into a future of increasing poverty, food shortages, conflict, and environmental degradation. But a growing group of demographers is convinced that the UN is wrong: the planet faces not a population bomb, but a population bust. For most of history, population decline has been the result of catastrophe—environmental events, famine, or disease. Now, however, fertility rates are falling for a different reason: we’re choosing to have fewer kids.
“In roughly three decades, the global population will begin to decline,” say Darrel Bricker and John Ibbitson in their new book EMPTY PLANET: The Shock of Global Population Decline. “Once that decline begins, it will never end.”
Empty Planet: Preparing for the Global Population Decline
The evidence given is that world nations have fallen below the replacement rate of each woman having 2.1 children. The world will reach a maximum population around 2050 of about 9 billion then it will start to decline.
The blame goes to urbanization. In rural settings children are a "blessing" because that means more hands to work the farm. In an urban setting, children are just another mouth to feed. So people as they urbanize are choosing to have less children for economic reasons.
Good for environmental reason, bad for economic reasons.
Fewer people means less economic growth. Fewer working age people having to support an aging population.