A new study by a Western University demographer shows that the happiness trajectories of new parents vary greatly depending on the age when people have their first child and how many children they have.

The findings of Rachel Margolis from Western's Faculty of Social Science and Mikko Myrskylä from the London School of Economics and Max Planck Institute for Demographic Research in Rostock, Germany, were recently published in the industry-leading journal, Demography.

The study, conducted using large data sets from Germany and the United Kingdom, showed parents' happiness increases in the year before and after the birth of a first child, it then quickly decreases and returns to their 'pre-child' level of happiness. Margolis says the fact that happiness increases just before and around the time of the birth suggests that this may capture not only the effect of the birth but also the broader process of childbearing, which may include partnership formation and making plans for the future.

Compared to men, women gain more in happiness in expectation of, and right after, the birth of a child. Women also have steeper drops in their happiness than men between the year of the birth and the year afterward, possibly because of the larger initial gain. However, in the long run, there are no differences between the happiness levels of men and women.

Margolis says that there are two main results. First, those who have children at an older age or who are more educated have a particularly positive response to a first birth. Older parents, between the ages of 35-49, have the strongest happiness gains around the time of birth and stay at a higher level of happiness after becoming parents. Those who become parents in their teens have a predominantly declining pattern of happiness that does not increase above the baseline even during the year of birth. Those who become parents between the ages of 23-34 have increasing happiness before a first birth, however one to two years after the birth, happiness decreases to baseline or below.

Second, parents' happiness trajectories differ based on which number child they are having. "What we see is that if a gain in parents' happiness is X-size for the first child, it's half of that for the second child and negligible for the third child," explains Margolis. "This means, in terms of happiness trajectory, the third child is statistically insignificant."

That's not to say parents shouldn't have three children, contends Margolis, but these findings suggest that happiness trajectories may at least partially explain ever-increasing low and late fertility rates.

Over the past 50 years, we have witnessed the global fertility transition, from high fertility towards low and late fertility. On average, people are having children later in life and having fewer of them. "The fact that among older and better-educated parents, well-being increases with childbearing, but the young and less-educated parents have flat or even downward happiness trajectories, may explain why postponing fertility and having only two children havedbecome so common" says Margolis.

The study utilized data from The British Household Panel Survey (BHPS) and the German Socio-Economic panel (SOEP).