Companies from Goldman Sachs Group Inc. to Monsanto Co. have gotten serious about making work more flexible. Thanks to apps and gadgets, you can easily tap away from a living room couch, the bleachers at your son¡¯s soccer game or huddled over a coconut on your Christmas vacation. There¡¯s a hidden cost to all this for women, though ¡ª and it isn¡¯t just the prospect of being available around the clock.

A recent working paper from the International Monetary Fund measured how much salary Japanese employees would be willing to forgo to enjoy a healthier work-life balance. It found that earners making ?3 million a year would give up nearly half of their income to avoid putting in 45 hours or more of overtime per month. That outcome was roughly consistent with higher-wage workers, too.

The most obvious takeaway would be that companies should do everything they can to keep hours reasonable. It doesn¡¯t take an MBA to see that lower salaries would improve the bottom line, with the added upside of happier and possibly more productive workers. There¡¯s an important caveat, however: Women are much more eager than men to give up money for time. That mostly comes down to deeper feelings of guilt, according to the paper, not just for child-rearing but also general household responsibilities such as cooking and caring for aging parents.