Why did early modern Japan evaluate land and raise taxes largely in rice, when medieval Japan was so famously awash in copper coinage? This puzzle, one that seems at first a bizarre case of “de-commercialization” during a period of what ought to have been intensifying commercial activity, has attracted a great deal of scholarly attention. Having read exactly one (1) book recently on the topic, Ōta Yukio’s Zeni odoru higashi shina kai (“When Coins Danced Upon the East China Sea”), I’d like to introduce what Ōta makes of the matter.

Copper coinage from China, especially the older, green-patina’d pre-Ming variety, became the standard currency across the Japanese islands by the 15th century. Expanding trade, driven by a simultaneous growth in demand for luxury goods in China, Japan, and Korea, spurred on the import of copper coin into the islands. This trade died down over the second half of the 15th century, as diplomatic snafus and other kerfuffles (largely caused by Japanese merchants) led to official reductions in the pace and scale of tribute missions to China, a major vector of commerce, and a general tightening of the Ming maritime ban. In the early 16th century, the discovery and exploitation of new silver mines in Japan, however, breathed new life into East Asian commerce. With demand for Japanese silver in China and Korea becoming a crucial motor for regional commerce, “illegal” trade by newly resurgent pirate organizations (called wakō) brought copper inflows to Japan to new heights. Silver, ironically, seemed to have solidified the place of copper within the Japanese economy.

All of this changed over the course of the 1560s. As the increasing violence of the wakō became a serious threat to the security of the southern Chinese coast, the Ming authorities embarked on a major crackdown on piracy, one that succeeded by the middle of the decade and effectively blocked the inflow of Japanese silver into the continent. In 1567, the Ming relaxed the maritime ban, allowing trade with southeast Asia but, significantly, not Japan. Via Manila, silver from the New World soon flooded into China, displacing the use of copper in Zhangzhou (to give one example) over the course of just a few years. With Japanese silver cut out of the picture of the China trade and the rapid American silver-ification of the Chinese economy underway, the flow of Chinese copper to Japan dried up.

The copper that remained in circulation was increasingly of very low quality, prompting a fresh wave of bans on “coin-picking,” referring to the long-standing practice of selectively accepting coin based on quality. To maximize circulation, local lords sought to prevent traders and other commercial actors from refusing “bad” copper, a policy later solidified under the Tokugawa, who in the first decades of the 17th century worked to “nominalize” the value of copper, treating all coins of the same denomination as worth the same, ignoring the vast differences in quality and purity of metal within the existing coinage. Unwilling to accept this situation, many in the west of Japan switched to accepting rice as currency for higher-value transactions over the 1570s.

In the east, high-quality coin had never circulated in great volume, encouraging the customary acceptance of “bad” coin at its nominal value from an early date. In this way, a “rice currency zone” developed in Japan’s west, while a “copper zone” remained intact in the east, with the boundary between the two zones somewhere in Ise. When the volume of bad copper in circulation eventually declined in eastern Japan, it endured as the unit of account for taxation and other transactions even when actual payments came to occur in rice, among other currencies. (This explains why some eastern domains like Sendai, for instance, recorded land value in copper kan rather than in koku of rice throughout the Edo period)

As an aside, this bifurcation in currency zones persisted throughout the early modern period. When the Tokugawa took control over Japan at the turn of the 17th century, they issued gold coinage to avoid the inflation in silver-denominated prices caused by the 16th century “silver rush.” Gold became the de facto major currency in eastern Japan during the Edo period, with silver, which had expanded its circulation along with rice in the late 16th century, taking on that role in the west.

Across the archipelago, copper scarcity prompted by the flooding of China with American silver made rice the standard measure of value during the crucial last decades of the 16th century, when key institutions of the early modern state (the cadastral survey, the kokudaka system of land evaluation etc.) were taking shape. Far from a sign of a shift away from the market, then, the standardization of rice as a unit of value and taxation was the product of 16th century Japan’s entanglement with the global economy.