Not only has the mass exodus of rural residents from the countryside in search of work impacted the children of migrant workers, it has also affected the elderly left behind. With the institution of the one-child policy in the 1970s, the average age in China has undergone an upward shift: 82% of migrant workers were between the ages of 15–44 in 2000. This has called into question the traditional custom of filial piety, and while retired urban workers are supported by government retirement programs, rural workers must rely on themselves and their families. It appears that the effects of migration on left behind elderly is ambiguous: while parents of migrant children are often better off financially and are happy with their economic situation, they also tend to report lower life satisfaction than do elderly without migrant children. Like the children of migrant workers, parents are known to experience psychological issues such as depression and loneliness, and those who take care of their grandchildren may feel burdened by this responsibility.