Americans work longer and weirder hours than anyone else, and inequality might be to blame.

Here are the facts: In 1979, Americans worked about as much as our European counterparts. But something happened in the intervening years: we've become a nation of workaholics, now logging an extra 250 to 400 more hours a year at the office Europe does. To put that in perspective, that's an additional six to ten weeks of work a year.

Not only do Americans work longer hours, though, but we also work worse ones. As you can see above, more of us are on the clock during nights and weekends than anyone across the pond.

Why? Well, the simple answer is that we work stranger hours just because we work longer ones. Simple, but not entirely correct. As Daniel Hamermesh and Elena Stancanelli point out, Americans who log more than 65 hours a week are 37 percent more likely to work nights and 44 percent more likely to work weekends than people who only work 40 hours. But there's more to it than that. When Hamermesh and Stancanelli looked at time-diary surveys for all these different workers, controlling for age, education, and immigrant status, they found that Americans would still be more likely to work at odd times even if we worked as little as the Europeans.

So Americans aren't just working outside the normal nine-to-five because they're working longer than that. There's something else making them rack up night and weekend hours — and that's pay. Indeed, companies have to offer higher pay to get people to work when nobody wants to. So it's no surprise that low-skill and immigrant workers, who need the extra money most, are the ones taking these jobs. That's also why there's more demand for this kind of overtime work here: we have more inequality and a less generous welfare state than other rich countries.

On the one hand, unlike countries that limit late-night work, it's good that we let people work when they need to. But on the other, it's sad that so many people do need to work weird hours just to make ends meet — and that we don't do more to help them.

Weekends are a luxury the bottom 30 percent can't afford.