The Koku System

If you’ve read anything about Shogunate-era Japan you’ve probably come across the term koku. It is mostly used to describe the wealth of an individual and measured in bales of rice. But this description significantly oversimplifies the implications of the koku situation and the effects it had on society. If your eyes aren’t glazing over already, then let’s dig into the details!

First some context: originally, the koku was defined as an amount of rice just under 280 litres. This was reckoned sufficient to feed one person for one year, and feudal domains were assessed in terms of their potential income in koku (their kokudaka). Samurai received a stipend several times a year in koku, and the amount of the stipend determined their status: a daimyo had to have an annual income in excess of 10,000 koku; a hatamoto received between 100 and 9,500 koku; while those receiving less than 100 were go-kenin. Koku also provided the basis for currency – one gold ryô was reckoned equivalent to one koku, and samurai often received part of their stipend in gold.

The income of a samurai in koku indirectly influenced what a samurai could be expected to provide for themselves or others. A 50-koku samurai could probably support his family and provide his own arms and equipment when called to serve; a 300-koku samurai would also be required to bring one go-kenin samurai, one spearman, one armour-bearer, one groom, one sandal-bearer, one hasamibako-bearer, and one baggage carrier as well as himself. As a result most samurai only actually saw about 1/3 of their potential income, the rest was paid to retainers or other expenses.

In terms of domains, their kokudaka partly determined their tax obligations and precedence at the Imperial court. The smallest domains produced 10,000 koku annually, while the most powerful domains could exceed 500,000 koku. Apart from the Shogun’s lands there was only one “million-koku” domain (modern-day Kanazawa). As a comparison, the Uwajima domain near where I live was worth 200,000 koku when Date Hidemune (eldest son of Date Masamune – yes, THAT Date Masamune, the one-eyed dragon himself) was assigned there to rule all of Iyo province (modern-day Ehime). It didn’t stay that way, because the Date family were not known for being slackers and layabouts. But that’s a story for another time, unfortunately…

Those are the basics of the koku system. But the implications of these things are where it gets more interesting.

Start with the obvious: rice is money. This means huge quantities of it have to be not only stored but distributed nationally. Taxes were based on rice and stipends paid in it, requiring a unified market (Osaka was the main center) and the associated national distribution and transportation system. Given the geography of Japan land transport was inefficient, so bulk cargoes mostly went by sea or river. This was usually handled by private merchants and carriers, sometimes supported and directed by government, and might explain why pirates were an ongoing threat around Iyo. At a more personal level, it’s difficult to slip a few koku into your pocket and go shopping. So those who could buy the rice and give you something more readily transferable in exchange (the merchants) had a degree of power greater than their official status would indicate.

The next point is equally obvious: people don’t just eat rice. Indeed they couldn’t: one koku was supposed to feed one person for one year, but it would not feed them well. Converted to modern figures you would get just over 1400 calories per day from this, while the recommendation for someone moderately active is 2000 and a quite active person (say a samurai or peasant) needs more like 3000. So supplementing their diet was essential for all concerned, especially at the lower end of the income scale.

From these points it should come as no surprise that the kokudaka of a domain often did not accurately represent their true wealth. It was seldom reviewed, and not infrequently deliberately biased. For example Tsushima was ranked at 100,000 koku when its agricultural output was actually below 10,000, simply because its importance in trade and foreign relations demanded a higher rank at court. In other cases higher kokudaka (and thus taxes) were assigned as a punishment, or an inspector could be persuaded to significantly under-report the productivity of a domain.

This infrequent reporting had some advantages. There was a strong incentive for everyone, from daimyo to peasant, to increase the output of the fields. When land became more available (through reclamation or irrigation) or more productive (through improved techniques) everyone involved benefited from the agricultural surplus thus created. This process continued throughout the Shogunate period, with the extra resources often being devoted to increasing the yields even more. And since only certain crops and factors were considered in the kokudaka assessment it encouraged diversification of produce and industries within a domain.

But it also came with a downside: only the individual domains really knew what their output was. This made it difficult for the central government to make plans and pushed more practical decision-making power to the provinces, who were naturally focused on their immediate local situation. Moreover, the tax system remained based on rice. As other products and industries became more important the economy shifted, resulting in the provincial and central governments facing financial crises while the merchants and farmers became increasingly wealthy. And this in turn led to inflation. A 50-koku stipend would have allowed a samurai and his family to live modestly but comfortably at the beginning of the period. At the time of the twilight samurai, however, they would have been living in poverty.

By the end of the Shogunate period, Japanese society was under a great deal of strain. The farmers and merchants rightly felt that their role in supporting the whole edifice was not recognised by the ruling samurai class. The samurai, meanwhile, resented the erosion of their power at the hands of those below them. Add in to this the stresses of increasing contact with the rest of the world, and it is no surprise that drastic changes would soon be underway. The koku of course can in no way be held responsible for this. At the same time, though, it’s hard not to speculate about whether a more flexible and fairly apportioned system might have eased some of the pressures of the period.

And for the writers among us this all has additional relevance. Next time someone gets paid in your story, pause and think about what this represents. What is the money based on? What can it get you? And what is this telling the reader about the society your characters live in?

Question of the post: The koku still survives in modern Japan as a unit of measure for the lumber industry. Should people hold on to these relics from earlier times, or is a standardised system of measurement a better idea?