Washington - A word of encouragement for working moms: You are actually more productive than your childless peers.

That's the conclusion of a recent study from the Federal Reserve Bank of St. Louis, which found that over the course of a 30-year career, mothers outperformed women without children at almost every stage of the game. In fact, mothers with at least two kids were the most productive of all.

Here's how the researchers, who were all men, came up with those results: They wanted to understand the impact of having children on highly skilled women, but their work is often difficult to quantify. How do you determine the productivity of a surgeon, a consultant or a project manager?

They decided to analyse the amount of research published by more than 10 000 academic economists as a proxy for performance. A job in the ivory tower of academia requires higher education by definition, and their work is easily searched, recorded and ranked.

The results were surprising. Among men, fathers of one child and those without children performed similarly throughout much of their careers. But men with two or more kids were more productive than both groups.

The effect for women was even more dramatic. Using their own method for analysing research publications, the authors found that within the first five or so years of their career, women who never have children substantially underperform those who do. (The difference in productivity between women with one child and those with no children is more muted, using a different ranking for research. But in both cases, mothers with at least two children perform the best.)

It's important to point out that the authors are examining a very narrow group of women with privileged circumstances. Parenthood was likely planned by many of them, with benefits such as maternity leave and paid sick time. They can also better afford to pay for resources like reliable childcare that allow them to work longer. Low-income or low-skilled mothers often face a very different working environment.

Even so, the results may seem counterintuitive for any working mom who has drowned herself with guilt over missing a deadline because a sick child had to go to the doctor.

Young children do take a toll on work. The paper found that there is a 15 to 17 percent drop in productivity among women with little kids. For those with multiple children, the first child results in a 9.5 percent drop in performance, the second child cuts out an additional 12.5 percent and the third child caps it off with an 11 percent decrease in productivity.

In other words, three preteens will result in a 33 percent loss in productivity on average, the equivalent of four years of research.

But as any parent knows, the days are long and the years are short. That's the case here, too. Mothers tend to be more productive both before and long after the birth of their children. When that work is smoothed out over the course of a career, the paper found, they are more productive on average than their peers.

“While you have small children, it has an impact on you,” said Christian Zimmerman, one of the paper's authors. “But after that, it seems that the impact is the other way.”

Indeed, Zimmerman said it's possible that the type of women most likely to have children, especially multiple kids, could also be the type of women most likely to succeed as academic economists. This is known as the “survivor bias.” Maybe their tenure and reputation are secure, making them feel more comfortable taking time out for family for a while. Or maybe they're just hyperorganised.

“If you want to do research and be successful at it, being well organised is a significant component of that,” he said. “That may be all that is driving the results.”

Washington Post