As regular readers know, I write about cost analysis because it fixes a major problem with cost-benefit analysis: it requires you to think about why a plan is good and why it is bad and make tradeoffs and tough choices. Cost analysis is black and white: we obsess over why an idea is bad so we can trash it without any regret about benefits we are sacrificing.
The basic idea in the Slate article is that, without flex time, women can either be career women or stay-at-home moms without much of a career.* Flex time gives women a third option with more work-life balance, but by opening the door for work-life balance some women choose to get out of the rat race and as a result (on average) women earn less, work fewer hours, and will ultimately have fewer top positions in their field.
The only problem I have with the article is this sentence:
This kind of work-life balance may make for happier women—consider the Netherlands, where women are quite happy . . .By acknowledging that flex time makes women happier you're acknowledging the tough tradeoff between happiness and money/prestige that women face. No one wants to hear about how you can't have a work 60 hours a week earning money and spend 8 hours a day with your family and get 8 hours of sleep.
* - This is an exaggeration. Obviously there are many ways to do some of each, so flex time really just expands women's options.