It's common knowledge that Americans tend to work longer hours than employees in other industrialized nations. Now a new study from researchers at the Royal Holloway University of London and the Paris School of Economics sheds some light on a less-discussed aspect of our workaholism: our propensity to work what the authors term "strange hours" - that is, late at night or on the weekends.

The study, by economists Daniel S. Hamermesh and Elena Stancanelli, compares the United States to a handful of wealthy Western European nations and finds that our labor force is fairly unique in its incidence of night and weekend work. I've charted out the authors' main findings below.

1. Americans work more hours than people in other industrialized countries, but it wasn't always this way.

In 1979, according to the OECD, Americans were roughly middle of the pack when it came to annual hours worked among the wealthy nations in the chart above. Fast-forward 33 years, and almost everyone's hours have actually dropped. But Americans' hours declined by the smallest amount, putting us at #1 among these countries.

Among all OECD nations, the full OECD dataset shows that Mexico works the longest hours. Korea, Chile and a handful of Eastern European countries also put in more annual work hours we do. But no wealthy Western European nations work longer hours than than the U.S.

2. Americans are less likely to work part-time, and more likely to put in long work weeks.

Part-time work is relatively uncommon in the U.S. - only 18 percent of U.S. workers put in fewer than 35 work hours per week. In contrast, 29 percent of Brits, 31 percent of Spaniards, and 44 percent of the Dutch do the same.

Conversely, about one in eight American workers put in more than 55 hours of work per week. Only one percent of the French work as long.

3. On average, the American work week is the longest.

Among the employed, Americans have the longest average work week, at 41 hours. The average Dutch work week is roughly nine hours shorter.

Narrowing the universe to only the full-time employed, a recent Gallup study found that the average full-time work week in the U.S. is 47 hours. This has changed little over the past ten years.

4. Nearly a third of Americans work on the weekend.

The U.S. has the highest incidence of people reporting any paid weekend work. 29 percent of Americans reported performing such work in the American Time Use Survey, more than three times the rate among Spanish workers.

It's important to note that this doesn't necessarily mean that these workers are working 9 to 5 every weekend, only that they reported performing paid weekend work in a time use survey. This would include things like going into the office for a few hours to finish up a project.

5. More than a quarter of Americans work at night.

27 percent of American workers report working nights, which the study defines rather strictly as any work performed between 10 PM and 6 AM. If the definition of "night" were expanded earlier into the evening, say 7 PM, this number would be considerably higher.

Overall the authors note that night and weekend work tends to be less desirable, as it is often performed by people with fewer skills and employers typically offer a premium wage for it. "American workers appear to be performing more work at less desirable times as well as working longer hours than their counterparts in other wealthy countries," they write.

The study finds no connection between long hours and strange hours - that is, Americans aren't working more nights and weekends simply because they work longer than people in other countries in general. "Whatever the explanations for the higher incidence of work at night and weekends in the U.S. than in Europe, its consequences may be quite dramatic in terms of fewer interactions with others and possibly worse health outcomes for Americans than Europeans," it concludes.