It’s no surprise that 73 hours a week, even done flexibly, are incompatible not only with family life, but also with anything else (that’s an important point, because the debate over work-life balance shouldn’t be just about how to have a career and be a mom — or dad for that matter — but also how to have a top job and still remain a human being). What’s more surprising is that it may also be incompatible with maximum productivity. A number of surveys show that working longer doesn’t necessarily mean working better (Slaughter cites a couple of them in her piece). In Germany, where labor-productivity rates are only a bit less than in the U.S. (and the economy prior to the euro crisis was more robust), workers spend about 80% of the time on the job that Americans do. For Germans, doing the job well is what matters; face time is less important. Indeed, a German executive a few years back once commented to me that “if you are at work past 6 p.m., there’s something wrong with you” (meaning, you simply aren’t being efficient enough). I can say personally that on the days when I know I need to be home for dinner, I work harder. On the days when I can leave at 10 p.m., I’m revving up more slowly.

It’s a truism that work expands to fit the time you give it. Indeed, the economic gains made in both the U.S. and Europe over the past two decades have been two-thirds productivity related and only one-third down to working more hours. Germans have managed to raise productivity substantially with much less increase in overall working hours. That’s in part because German workers have much, much more control over their circumstances than Americans do. Labor representatives sit on the boards of most major German companies. Their relationship with management is more collaborative than contentious. They work together to figure out ways to keep productivity up while not killing people.