They're at the center of human history. In the early part of the Ming Dynasty, Chinese farmers paid their taxes in goods, mainly grain and labor. But as more silver entered the economy, the Ming government changed its policy and required taxes to be paid in silver. This meant that almost everyone in China had to produce something that could be sold for silver, which usually meant silk. In fact, the Ming government often required people to make silk. That glut of silk inevitably led to a price drop, which hurt the Chinese economy, but not nearly as much as it hurt the Spanish economy, where almost every silk producer was put out of business. So much for the idea that global outsourcing is a new problem.