Victory for the American worker! It's a long read, but Sara Robinson's article from Alternet (reposted on Salon) looking at the history of the length of the work week in the era following the Industrial Revolution is an interesting read, especially if you've worked for an employer that routinely pushed you to extend your work day past the eight hour barrier on a regular basis:

Most modern-day managers assume there will be a direct one-to-one correlation between extra hours and extra output, but they’re almost always wrong about this. In fact, the numbers may typically be something closer to 25-30 percent more work in 50 percent more time.

Here’s why. By the eighth hour of the day, people’s best work is usually already behind them (typically turned in between hours 2 and 6). In Hour 9, as fatigue sets in, they’re only going to deliver a fraction of their usual capacity. And with every extra hour beyond that, the workers’ productivity level continues to drop, until at around 10 or 12 hours they hit full exhaustion.