"Children may be a long-term investment in happiness," says MPIDR demographer¹ Mikko Myrskylä. Together with Rachel Margolis from the University of Pennsylvania in Philadelphia, USA, he published the new study in the latest issue of the journal "Population and Development Review". It shows a global trend: while for parents under 30 the level of happiness decreases with the first and each additional child, mothers and fathers aged² 30 to 39 feel as happy as childless peers until they have four children or more. From age 40 onwards parents are even more content than childless couples are unless they have more than three children. Mothers and fathers over 50 are generally happier than their childless peers, no matter how numerous their offspring（后代，子孙） . With a sound data basis, this study clarifies for the first time the discrepancy³（不符，矛盾） between the widespread belief that children bring happiness and the fact that most research finds either a negative or no significant relationship between parenthood and well being. "Seeing the age trend of happiness independent of sex, income, partnership⁴ status and even fertility rates shows that one has to explain it from the perspective of the stage of parents life", says Mikko Myrskylä who at the MPIDR is heading the Max Planck Research Group "Lifecourse Dynamics⁵ and Demographic Change".

In the early stages of parenting, positive aspects of having children are overshadowed by negative experiences such as lack of sleep, concerns about the child's well being, and financial strains（资金紧张） . The older parents get, the less they feel such pressure caused by their offspring as the child grows up and becomes more independent. When children reach adulthood⁶ their parents, who are then between 40 and 60 years old, can benefit from them financially and emotionally. Consistently, the study finds that the satisfaction of parents over 40 rises with the number of children comparatively strongly in former socialist⁷ states. Welfare systems in these countries are less far developed and parents depend more on direct financial support from their children.

Governments also play a role in enhancing the happiness of young parents. In former socialist countries like Russia, Poland and Hungary that offer limited support for parents of young children, their contentment compared to childless peers decreases particularly strongly with the number of children. In contrast, the curve is rather flat in countries with more developed welfare states like Western Germany, Austria and Switzerland. In these countries peers with and without children feel similarly well at any age. At the same time the influence of children as a source of happiness seems to be rising over time. From 1997 to 2005 parents of all ages reported feeling happier than they did in the period from 1981 to 1996.

The results of this study are based on data from more than 200,000 women and men over fifteen years old questioned for the World Value Surveys (WVS) from 1981 to 2005. The WVS is the largest international survey including questions concerning happiness and fertility.