There are many social, cultural, religious and economic reasons why parents in the developing world have large families. Access to contraception and education on family planning is often limited. There are often no government provided pensions or social security benefits, so parents must rely on their children to care for them in their old age. Because child mortality rates in the developing world are so high, parents will often have many children in the hope that some will survive to provide that support. The need for extra labour in largely agricultural societies, a cultural expectation to have many children, and a preference for boys over girls are other reasons why large families are common in the developing world.