Amid the Father's Day festivities, many of us are privately asking a Scroogely question: "Having kids—what's in it for me?" An economic perspective on happiness, nature and nurture provides an answer: Parents' sacrifice is much smaller than it looks, and much larger than it has to be.

Most of us believe that kids used to be a valuable economic asset. They worked the farm, and supported you in retirement. In the modern world, the story goes, the economic benefits of having kids seem to have faded away. While parents today make massive personal and financial sacrifices, children barely reciprocate. When they're young, kids monopolize the remote and complain about the food, but do little to help around the house; when you're old, kids forget to return your calls and ignore your advice, but take it for granted that you'll continue to pay your own bills.

Many conclude that if you value your happiness and spending money, the only way to win the modern parenting game is not to play. Low fertility looks like a sign that we've finally grasped the winning strategy. In almost all developed nations, the total fertility rate—the number of children the average woman can expect to have in her lifetime—is well below the replacement rate of 2.1 children. (The U.S. is a bit of an outlier, with a rate just around replacement.) Empirical happiness research seems to validate this pessimism about parenting: All else equal, people with kids are indeed less happy than people without.

While the popular and the academic cases against kids have a kernel of truth, both lack perspective. By historical standards, modern parents get a remarkably good deal. When economist Ted Bergstrom of the University of California, Santa Barbara reviewed the anthropological evidence, he found that in traditional societies, kids don't pay. Among hunter-gatherers, children consume more calories than they produce, and grandparents produce more calories than they consume virtually until the day they die. Agricultural societies are much the same. Only in recent decades did people start living long enough to collect much of a "pension" from their kids. While big financial transfers from children to their parents remain rare, only in the modern world can retirees expect to enjoy two decades of their descendents' company and in-kind assistance.

It's also true that modern parents are less happy than their childless counterparts. But happiness researchers rarely emphasize how small the happiness gap is. Suppose you take the National Opinion Research Center's canonical General Social Survey, and compare Americans with the same age, marital status and church attendance. (These controls are vital, because older, married and church-going people have more happiness and more kids). Then every additional child makes parents just 1.3 percentage points less likely to be "very happy." In contrast, the estimated happiness boost of marriage is about 18 percentage points; couples probably have fewer highs after they wed, but the security and companionship more than compensate. In the data, the people to pity are singles, not parents.