Framed by the decline of the Heian aristocracy in the late 1100s and the rise of the Tokugawa shogunate in the early 1600s, Japan's medieval era was a chaotic period of diffuse political power and frequent military strife. This instability prevented central authorities from regulating trade, issuing currency, enforcing contracts, or guaranteeing property rights. But the lack of a strong central government did not inhibit economic growth. Rather,...