At the beginning of the 1500s, China had an isolationist trade policy, which meant that trading with foreigners was not allowed, but the policy changed during the course of the century until the merchant class became powerful and rich. Although previous dynasties allowed imperial trade, the Ming Dynasty kept China to itself for the most part.
In the middle of the 1500s, China reversed its trade policy, and trade with foreigners became encouraged. The middle class grew and prospered and, in general, the Chinese people had more freedom to work as they wished. There was also a blurring of class lines during this period as well. Not only did merchants begin to prosper, but so did farmers. With money and education, the government permitted these classes to take the Imperial Examination, and enter government. The dynasty prospered for the next 70 years, but it was very reliant on foreign trade.