BEIJING, CHINA - JULY 7: Pedestrians walk past a billboard reading "Control population growth, and raise the quality of the population" July 7, 2003 in Beijing, China. In an effort to control the rapid growth of China's population, the government implemented a single-child policy in the 1970s, aiming to keep the population below 1.6 billion by 2050 with zero population growth. China now has nearly 1.3 billion people, making it the most populated country in the world. The United Nations Population Fund had declared July 11 World Population Day, focusing on the concerns of the nearly 3 billion people under the age of 25. (Photo by Natalie Behring-Chisholm/Getty Images)
