Elderly parents in China can now sue their grown children for both financial and emotional support.

The changes in the law in China reflect an increasingly urgent dilemma across the world: As populations age faster than ever before, families and governments are struggling to decide who will protect and provide for the old. Too often, the answer is nobody.

The Associated Press spent months reporting across formats on population aging and the growing problem of elder abuse and neglect for an occasional series, Old World. Here are five things to know about the situation in China, where filial piety, or respect for one's parents, was once a given:

HONOR THY FATHER AND MOTHER - IT'S THE LAW

A handful of countries, such as China, India, France and Ukraine, require adult children to financially support their parents. Similar laws are in place in 29 U.S. states, Puerto Rico and most of Canada, but they are rarely enforced because government aid helps support the old. In Singapore, adult children who do not give their parents an allowance can face six months in jail.

HONEY, SO NICE THAT YOU CAME

More than 1,000 parents in China have sued their children for financial support over the last 15 years. But the law now goes further to require that adult children regularly visit their parents. Employers are required to give workers time off to do so, although that provision may be hard to enforce.

GOING GRAY BEFORE GETTING RICH

China is not yet wealthy enough to keep up with its rapidly aging population. It is projected to have 636 million people over age 50 by 2050, or nearly 49 percent of the population — up from 25 percent in 2010. Although a recent expansion of the medical system covers most Chinese, reimbursement rates remain low and out-of-pocket costs high. Many rural families cannot afford hospitals' huge up-front deposits.

THE FIRST AMONG 100 VIRTUES

A Chinese proverb calls filial piety, or respect for one's parents, "the first among 100 virtues." The ancient philosopher Confucius credited it as the bedrock of social harmony, and a popular song urges grown children to visit their parents often. Communities hold "best children" contests, complete with cash prizes. One county even made filial piety a condition for the promotion of local officials. And generations of Chinese have read the classic morality guide, "The Twenty-Four Filial Exemplars," where sons strangle tigers, let mosquitoes feast on their blood and proudly scrub bedpans for the sake of their parents.

AT HOME OR AWAY

Nursing homes are not an option for most Chinese. The few nursing homes in China supply only 22 beds for every 1,000 seniors, and most are too expensive for the average family. Even children who can afford nursing homes fear sending their parents away will mark them as un-filial.