Unemployment

Just read an interesting paragraph in an essay about the internet bubble:

The prospect of technological leverage will of course raise the specter of unemployment. I'm surprised people still worry about this. After centuries of supposedly job-killing innovations, the number of jobs is within ten percent of the number of people who want them. This can't be a coincidence. There must be some kind of balancing mechanism.

From Paul Graham. He's probably right, but it seems possible that the mechanism is people bitching about being unemployed and holding society effectively at ransom to find jobs for them to do. (i.e. a country that has 50% unemployment usually has social unrest, too, and some sort of reforms are proposed so that the rich people and companies can get back to making money without that pesky mob at the front gate.) Probably there's someone who studies this; it would be interesting to know whether my idea is right.