The Edo-Period Financial System - Money Changers as 'Banks'
During the Edo period (1603-1868), Japan had "ryogae-sho" (money changers) that served as the equivalent of modern banks. Their original business was exchanging three types of currency - gold coins (koban), silver coins (chogin), and copper coins (Kan'ei Tsuho) - but they gradually expanded into accepting deposits, making loans, and handling kawase (remittances to distant locations). Major money changers in Osaka, such as Konoike Zen'emon, Tennojiya Gohei, and Hiranoya Gohei, amassed enormous wealth through loans to feudal domains.
Money changers' lending rates fluctuated based on shogunate regulations and market supply and demand. General lending rates were approximately 12-18% per year, but loans to daimyo (feudal lords) carried lower rates of about 8-12% due to lower credit risk, while small loans to commoners could reach 20-48% annually. Compared to the modern consumer finance cap rate of 20% per year in Japan, the rates charged to Edo-period commoners were remarkably high.
The Shogunate's Interest Restriction Edicts - Attempts to Stop Compounding's Runaway
The Edo shogunate issued interest restriction edicts on multiple occasions. During the Kyoho Reforms (1716-1745), the 8th Shogun Tokugawa Yoshimune limited interest on monetary loans to 15% per year or less. Even more significantly, the shogunate prohibited juri (重利) - compound interest. It banned the practice of charging interest on interest and mandated simple interest calculations.
Behind this compound interest ban was the reality that samurai and farmers were going bankrupt in droves due to the snowball-like expansion of their debts. At 15% compound interest left for 5 years, the principal roughly doubles. At 20%, it grows to about 2.5 times. For samurai and farmers whose incomes were not increasing, debt expanding through compounding was a direct cause of insolvency. The shogunate's compound interest ban was born from the same concern as the interest restrictions in the Code of Hammurabi 3,800 years earlier.
Daimyo Loans and Domain Fiscal Collapse - Compound Interest at the National Level
Edo-period domain finances bore a striking structural resemblance to modern national finances. Many domains fell into chronic fiscal deficits due to the costs of sankin-kotai (alternate attendance in Edo), maintenance of Edo residences, and disaster response, becoming dependent on borrowing from money changers. Interest on borrowings squeezed domain revenues, and borrowing more to pay interest created a vicious cycle.
The Satsuma domain (present-day Kagoshima Prefecture) carried debts of approximately 5 million ryo by the end of the Edo period. With annual domain revenue of about 140,000 ryo, this represented roughly 36 years' worth of income in debt. This was far more severe than Japan's current government bond balance (approximately 2 times GDP, or about 2 years of national income). Satsuma's chief retainer Zusho Hirosato restructured the domain's finances by converting the debt into a 250-year installment plan (effectively a default). It was, in a sense, a reverse application of compounding - using time as an ally to resolve debt that had ballooned through compound interest.Books on Edo-period economic history contain even more detailed accounts of the relationship between domain finances and money changers.
The Meiji Restoration and Modern Banking - The Day Compound Interest Was 'Officially' Legalized
After the Meiji Restoration of 1868, Japan rapidly established a modern financial system. The National Bank Act was enacted in 1872, and the Bank of Japan was established in 1882. With the introduction of the modern banking system, interest payments on deposits were institutionalized, and compound interest calculations were officially recognized. The juri (compound interest) that had been banned during the Edo period was legitimately revived within the framework of modern finance.
Deposit interest rates during the Meiji era were approximately 5-8% per year - incomparably higher than today's low-rate environment. At these rates with compound interest, assets would grow 1.6 to 2.2 times in 10 years. Meiji-era Japanese could experience the benefits of compounding simply by making deposits. In modern Japan, with deposit rates near zero, investment in equities or mutual funds is necessary to benefit from compounding. Over 400 years, the means of harnessing compound interest have changed, but the principle of "time x interest rate = asset growth" remains immutable.
Next Actions - Lessons from 400 Years of History
From Edo-period money changers to today's NISA, the history of Japanese finance is a continuous series of experiments in "how to make compound interest your ally." Edo-period samurai suffered from the enemy side of compounding (high-interest debt), while Meiji-era depositors enjoyed the ally side (high-interest deposits). Today, we cannot benefit from compounding through deposits alone, but we possess powerful tools that did not exist 400 years ago - NISA and index funds. What history teaches is that while the mathematics of compounding never changes, the optimal means of harnessing it evolves with the times. Use a compound interest calculator to confirm the best way to leverage compounding in the current era.