After all the years of worrying about a population explosion, scientists now say populations are shrinking, or will soon do so because of falling fertility rates in both developed and developing nations. That presents a new set of problems for societies. 

One of the few exceptions to this trend is the United States, where fertility rates have not dropped as much and which benefits from continued immigration. In this video series, Leta Hong Fincher examines these startling demographic developments.

Experts: Falling Birth Rates to Cause 'Demographic Time Bomb'

The global population has experienced an unprecedented reduction in birth rates over the past few decades. People in rich and poor countries alike are having fewer babies, which demographers warn will lead to a worsening problem of global aging.

Fewer Babies, Rising Longevity Lead to Global Aging Crisis

Almost everywhere in the world, people are having fewer and fewer babies. How will Europe, Japan and the United States cope with providing for the elderly? And how might demographic changes reshape developing countries in the Middle East and Africa?

US Population Stable Due to Higher Birth Rate and Immigration

Most of the rich, developed countries in the world are facing an aging crisis, as their fertility rates fall to unprecedented lows. But analysts say the United States is better equipped to deal with the challenges of aging than almost any other developed country--thanks to its relatively high birth rates and immigration.