Koku

The basic monetary unit in feudal Japan was the koku. Historically, it is based on the amount of rice needed to feed one adult person for one year, about 180 liters, or 5 bushels.

Taxes and revenues were calculated in terms of koku. A farmer usually paid 40-60% of rice production, or its equivalent, as tax to the lord of the fiefdom. The amount of tax in koku was determined every time there was a survey to estimate the yield. This helped the government budget their spending as they knew the amount of expected revenue. If the farmer produced more than the assessed value, he simply kept the proceeds, and saved them for a rainy day.

"Watermill at Onden" polishing rice --From the woodblock print series 36 Views of Mount Fuji by Katsushika Hokusai (1760–1849)

The basic unit of a rice field is the cho, which is about 2.5 acres. Yield depended of many factors, of course, but one rule of thumb they may have used to assess production value is: one cho produces 10 koku of rice per harvest, requiring 4 or 5 man-years of labor.

Over time brokerage services developed, and the head man of the village, after keeping the amount needed by the village, arranged with the rice brokers to buy the rest of the harvest, pay the lord the taxable amount, and remit any remaining amount to the village.

"Edo Nihonbashi" rice brokers --From the woodblock print series 36 Views of Mount Fuji by Katsushika Hokusai (1760–1849)

The yield of a rice field, is affected by many variables:

• Rain, or water supply
• Natural disasters
• Quality of terrain
• Pestilence (rats or insects)
• Disease
• Quality of labor
• Available technology
• Higher-yield rice strains

A stalk of rice is grown from one grain of rice. As each stalk produces over one hundred grains, less than 1% of the harvest need to be saved for the next planting. As time went on, production of rice per acreage increased significantly, due to new strains of rice that produced higher yields, allowing for a higher standard of living for the farmers.

In favorable conditions, a farmer could grow a second crop on the land outside of the rice-growing season, such as rapeseed for oil. Farmers usually also planted other produce on dry area, such as fruits and vegetables, and even commercial crops such as tea or cotton.

A farmer in a poorly-governed domain may have had to pay for protection from local bandit gangs, affecting his profitability.

The bale of rice that you see in samurai movies and TV shows is two-fifth of a koku, which is about 90 pounds, or 40 kilograms.

Using modern Japanese figures, one koku of rice provides about 1430 calories per day per person. Although rice is a good source of protein, it does not provide all the nutrients required to maintain good health. The traditional Japanese diet also includes fish, other seafood including roe and seaweed, fowl, eggs, soy bean products including tofu and miso, other beans, fruits, nuts, other cereals such as millet and buckwheat, tea, saké, salt and other seasonings including soy sauce, mushrooms, potatoes, and many varieties of vegetables. Since Buddhism discourages the killing of animals, meat consumption was rare, except for venison and wild boar in places where rice could not be harvested.

Coinage

Traditionally one koku of rice equaled one ryo of money, which was represented by a gold coin called a koban. A koban had a fixed weight of 18.2 grams, or 0.64 ounces of gold. At present exchange rates of about US$1,200 per ounce of gold, one ryo, or one koku, is therefore worth about US$800 in today's money. Ergo the lowest- ranked daimyo with a fief worth 10,000 koku had an income of about US$8 million per year.

Senryo-bako "Thousand ryo box" used for transporting 1,000 koban

The rates of exchange, however, fluctuated greatly. If there was a poor harvest, the cost of rice in the region would rise accordingly. Speculators would also cause spikes in rice prices. As finances of the samurai class worsened, coinage was devalued when they started replacing a certain percentage of the gold in the coins with other metals, forcing re-evaluations of the cost of rice and exchange rates with other coinage. Papinot claims that in 1787 one koku of rice cost 5.5 ryo.

Koban

Values between gold, silver, and copper fluctuated throughout history. The following are plausible rules-of-thumb for feudal Japan:

• 1 oban = 10 koban = 10 ryo
• 1 koban (oval gold coin) = 1 ryo
• 1 ryo = 4 bu (rectangular silver coin) = 16 shu = 4,000 mon or zeni (round copper coin with a small square hole)
• 1 ryo = 60 monme (silver coin weighing 3.75 grams, or 0.13 ounces)
• 1 ryo = US$800 (based on US$1,200 per ounce of gold)
• 1 monme = US$13.33
• 1 mon or zeni = US$0.20

Top left: gold koban Bottom left: gold bun Top right: silver bun Middle right: silver shu Bottom right: copper or bronze mon or zeni

A cup of tea at a rest stop would cost 1 or 2 mon.

The copper mon had a hole in the middle which allowed them to be strung together in quantities of 100 or 1,000, the latter equal to 1 bu, or 1/4 of a ryo.

String of 100 mon coins, about US$20 today.

In terms of weight, 1 ounce of gold equaled over 12 ounces of silver in feudal Japan, which meant silver was worth almost US$100 per ounce in today's money, which is much higher than today's value of less than US$18 per ounce of silver. If you assume gold price today is US$1,200 per ounce, this means one ounce of gold today is equal to around 70 ounces of silver. From the point of view of today's silver prices, the gold koban would be worth only a little more than US$200 per ounce.

In terms of cost of rice today, a bushel of rice weighs about 45 pounds, so five bushels, or one koku, is 225 pounds of rice. Regular non-premium Japanese-style short-grain rice at the supermarket today costs about $1 per pound, so a koku of rice today would cost roughly US$225.

Source

• Wikipedia

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