(Photo: Kevin Baird/Flickr)

Having a baby is the most wonderful, joyous, perfect, wonderful journey you'll ever embark on. Yeah, right. New parents are generally less happy in the year after a first child is born—a fact that may also explain declining fertility rates in developed countries, according to a new study out of Germany.

Germany achieved a world record low birth rate in recent years—only 8.2 births per 1,000 residents every year, just edging out Japan's 8.4. On average, German women have about 1.4 children over the course of their lives, a number too small to maintain the country's current population or, for that matter, its workforce. (By comparison, the United States' average is 13 births per 1,000 residents every year, and 1.9 children per woman, according to World Bank statistics.) Why is the birth rate so low? Oftentimes, the answer has something to do with the increasing number of women in the workforce, some of whom may choose to delay having kids, or to forgo them altogether. But even if that's true—and it's not entirely clear that it is—the emphasis on working women might overlook other important reasons.

German women have about 1.4 children over the course of their lives, a number too small to maintain the country's current workforce.

In particular, that explanation overlooks the happiness factor, according to demographers Rachel Margolis and Mikko Myrskylä. The pair were motivated to investigate happiness' role in fertility in part by a 2008 study, in which a researcher found that parents' experiences with their first children had something to do with how large their families ultimately became. Still, that conclusion was based only on interviews. For harder data, Margolis and Myrskylä turned to the German Socio-Economic Panel Study, an annual survey of 11,000 households that's been running since 1984. In particular, Margolis and Myrskylä looked for data indicating when survey participants had their first child, when or if they had a second, and asked one simple question: On a scale of zero to 10, how satisfied are you with your life?

Overall satisfaction, either before or after having a first child, didn't have much to do with whether parents decided to have a second. But, the researchers found, a drop in life satisfaction did make a difference. Margolis and Myrskylä estimate that only around half of the people who report a drop of three points or more on the satisfaction scale have a second child, a decline of 10 percentage points compared with those who reported no change in satisfaction.

Perhaps more interesting are the factors associated with declines in satisfaction after the first child—and just how large those drops are. Women and people with less income or education showed the biggest declines in life satisfaction. Overall, 37 percent of those surveyed reported a one-point drop, 19 percent reported a two-point drop, and 17 percent reported a three-point drop or more—numbers that might start to explain why Germans (and others) are having fewer and fewer kids.

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