资料题：To parents who take the responsibility for children's expenses, the cost of living increases because（　）。

In the past, American families tended to be quite large.Parents raising five or more children were common.Over the years, the size of the family has decreased.One reason for this is an increase in the cost of living.On the average, children attend school for more years than they used to, making them financially dependent on their families longer.Moreover, children nowadays are better dressed and have more money to spend on entertainment.The parents usually take the responsibility for all the expenses.Meanwhile, families are less close than they used to be.More and more American mothers work away from home.The breakup of the family occurs when the parents divorce.A lot of children in the U.S.live part of their young lives with only one parent.Broken families usually result in problems for children and parents alike.Children blame themselves when their parents separate.They grow up feeling unsettled as they are moved back and forth between parents .Usually one parent is responsible for raising thechildren.These single parents must cane for the children's emotional and psychological needs while also supporting them financially.This is very demanding and leaves very little time for the parent's own personal interests.Single parents often many other single parents.In this type of family, unrelated children are forced to develop brother or sister relationship.The situations of many American families today are not good.However, recent signs indicate that things are getting better.The divorce rate is declining.The rate of childbirth is rising.Perhaps Americans have learned how important families are.