Now, China didn't have a lot of silver itself, but Japan did, so they traded manufactured goods for it, but soon even that wasn't enough. This was mostly because in the 16th century, China changed its tax structure. Taxes, man! 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.