China today is home to 13 billion people--nearly one quarter of the world's population. The growth of China's population is largely the result of modernization, which has brought with it more food, better medical care, less disease, and fewer epidemics and famines. The death rate in China has decreased, and more children survive. The higher survival rate in China means that more people are entering childbearing age. This population growth was threatening to destroy China's chances to become a richer country: just providing food and basic necessities for everyone would consume all of its economic gains. To tame the explosive population growth, the Chinese government launched a drastic policy of allowing one child per family. To enforce this policy, the government has a variety of incentives for those who comply and punishment for those who do not. For example, couples who have only one child get a monthly pay until the child is fourteen, special consideration for scarce housing, free medical care, and extra pension benefits. The pressure to conform. is powerful. Couples who ignore the state's directive suffer social disgrace and economic penalties. The family-planning policy, instituted in China in 1979, has been remarkably effective (though considerably more so in cities than in the countryside). Births to women of childbearing age have fallen dramatically--to about 2.5 children for every woman. China may eventually succeed in balancing its population growth, but in doing so, it is creating a new problem. The irony is that because of the very success of China's population policy, the Chinese population is aging rapidly. In 1982, 5% of the population was over age 64. In 2010, about 9% will be over 64, and in 2050, 25% will be. At the family level, children without brothers or sisters will each have to care for two aging parents. At the national level, the great numbers of aging people will tax the society's resources. China shares this problem--a rapidly aging population with- out a large enough following generation to support it--with many of the developed nations of the world. The primary purpose of this passage is to ______.