My wife and I are expecting a baby girl in September, and Daniel Hamermesh has a scary message for soon-to-be parents like us: The impact that a new baby has on your pocketbook is trumped by the impact on your stress levels. In a new study, Hamermesh, an economist at the University of Texas at Austin, translates that stress into dollar figures and finds it is “so huge as to be almost unbelievable,” he told me. (Gulp.)

In fact, the stress costs are so large, Hamermesh argues, that our family would need a lot more income to compensate. “If we thought about it more, we’d have fewer kids,” he said. (Gasp.)

Hamermesh and his co-authors quantify these stress effects in their recent working paper, “The Stress Cost of Children.” Although the paper has not yet been peer-reviewed, the results are startling. Parents’ self-reported feelings of financial stress increase little after having a child. But time stress — or how overwhelmed and rushed parents feel — jumps enormously, especially for mothers, and it lasts several years. Translating that time stress into dollar figures shows that having a child produces a significant burden — on top of the $245,340 in food, housing, education and other costs that the U.S. Department of Agriculture estimates that it takes to raise a kid.

To make these calculations, Hamermesh and his co-authors used two massive longitudinal studies from Australia and Germany, each spanning more than a decade: the Household, Income and Labour Dynamics in Australia (HILDA) survey and the German Socio-Economic Panel (SOEP). (The researchers would have liked to study the United States, but similar longitudinal data doesn’t exist here.) Both the Australian and German surveys followed more than 7,000 heterosexual married couples for roughly a decade through 2012 and routinely asked participants questions like “How often do you feel rushed or pressed for time?” The participants were also asked to rank their satisfaction with their financial situation. The researchers looked at how stress levels changed for couples who had a child during the study period compared with those who didn’t. Despite differences in culture and child-care services between Australia and Germany, the qualitative conclusions from both studies were similar. That suggests the results “supersede any cultural or legislative differences,” Hamermesh said.

Those conclusions show — perhaps unsurprisingly — that the stress burden of a new kid falls heaviest on the mother. Specifically, a mother’s self-reported time stress increases about 20 percent to 22 percent in the first year or two after a child’s birth. Time stress rises far less for fathers, between 5 percent and 8 percent. The time stress on the mother, furthermore, doesn’t fade during the first few years of the child’s life, while it does for the father. “If I were a feminist, I would love this,” Hamermesh said.

Comparable research is hard to find. Troves of studies have examined how happiness changes for parents upon having a child. And those are similarly based on self-reported responses to surveys asking questions like “How happy are you?” and “How satisfied are you with your life?” But Hamermesh is skeptical of happiness statistics. “I don’t know what it means,” he said, “and it’s not clear what the heck it measures.” He argued that self-reported happiness is more squishy than self-reported stress.

Those happiness researchers, however, might see Hamermesh’s approach as incomplete. Peder Pedersen, who is an economist at Aarhus University in Denmark and has studied the effect of a new child on parental happiness, said in an email that “it’s absolutely valid to study stress and financial costs” but that doing so is not a “substitute for a well-being measure.” Another economist in this field, Kevin Staub of the University of Melbourne in Australia, said in an email that he sees the Hamermesh paper as an “exciting addition” to the literature, but he added that studying stress does not imply that happiness measures are invalid.

Regardless of whether happiness is a more complete indicator of how parents feel after they have children, the real innovation of Hamermesh’s paper is how he and his co-authors put a price on the time stress. Since they knew mothers experienced more time stress than fathers, they tried to answer the same basic question: How much money would it take to reduce a mother’s financial stress enough to offset the increase in her time stress?

Specifically, the researchers normalized time stress and financial stress into a common unit of analysis and considered both types of stress as reciprocal components of parents’ overall stress. From the survey data, they already knew how much time stress went up after a kid entered the picture; they then calculated by how much financial stress would have to fall to offset that rise.

Using the Australian survey data, the researchers found that to offset a new mother’s time stress, her annual earnings would have to increase by about $66,000 (or her husband’s earnings would have to increase by $163,000). Using the German survey produces more modest estimates: A mother would need a $48,000 annual raise to offset her time stress (or she’d need to see her husband get a $55,000 raise instead). As you can see, a mother responds differently to changes in her income than to changes in her husband’s — that’s because a $1 increase in her earnings goes further in reducing her stress than a $1 increase in her husband’s.

There are a number of confounding factors in studying how parents respond to a new child. (This study didn’t follow couples for more than three or four years; the effects beyond that period are unclear.) For one, couples who plan to have a child may do so when their stress is low. Sure enough, this paper documents a dip in self-reported time stress for women and in financial stress for men in the year before a child’s birth. Hamermesh and his co-authors readily admit that they couldn’t completely control for these factors, but “if anything, we underestimate the [stress] effect following the birth,” Hamermesh said. (Another gulp.)

So what can we do to help stressed-out parents? Hamermesh and his co-authors believe extra help with child care can alleviate the stress of having a kid — but only so much. Their estimates show that even if women were able to eliminate their child-care and child-related housework responsibilities following the birth of a child, they would still experience higher time stress. Hamermesh said that it’s “just having the buggers around,” to say nothing of the work they require, that stresses parents out. (Sigh.)

But if having a kid is so stressful, and that has real, quantifiable costs, why do people do it? “The long-term gain must exceed the short-term cost,” Hamermesh said, before adding earnestly: “Not having a third kid is a great regret of my life.” (Whew.)