- Japanese: 石高 (kokudaka)
Kokudaka was a measure of the agricultural production of a daimyô domain, or "han," expressed as a measure of koku of rice. As a representation of the domain's wealth, kokudaka determined the amount of the domain's tax obligations to the shogunate, and the domain's status relative to other domains.
The smallest daimyô domains, by definition, possessed at least 10,000 koku, while some samurai retainers were granted sub-domains within a han, with a much smaller rating in koku. The majority of han were officially assessed at a kokudaka in the range of 10,000 to 200,000 koku, though the kokudaka of the most powerful domains exceeded 500,000 koku.
This figure, though ostensibly based on the actual agricultural production of the domain's territory, often did not change over the course of the period. A domain's kokudaka might be changed as a political reward or punishment, but the shogunate did not engage in regular surveys of agricultural production, and did not update domains' kokudaka on the basis of their production.
Multiple different figures for the kokudaka thus often existed simultaneously for a single domain. The official figure determined and recognized by the Tokugawa shogunate and used as a marker or indicator of the domain's wealth and status can be referred to as omotedaka (表高), using the character omote, meaning "official," "surface," or "outside." Meanwhile, nearly all domains maintained their own internal figures for agricultural production, called uchidaka (内高), using the character uchi, meaning "inside" or "internal." The uchidaka was often a higher figure, more regularly assessed and more accurately reflecting increases and expansions of agricultural productivity within the domain. It was generally in the best interests of the domain to not report the higher figure, and to allow the omotedaka recognized by the shogunate to remain at a lower figure, since this meant lower tax payments owed by the domain to the shogunate; though this seems deceitful or deceptive, such behavior was widely condoned by the shogunate, as part of the philosophy of omote and uchi, allowing internal matters to remain relatively private, so long as a domain's obligations on the official, external level were properly observed.
Examples of Omotedaka
- Kaga han - 1,000,000 koku
- Satsuma han - 770,000 koku
- Hiroshima han - originally 498,000 koku, later 426,500 koku
- Morioka han - 100,000 koku, doubled to 200,000 in 1808 in recognition of its contributions to the defense of the realm
- Tsushima han - 100,000 koku, due to its great diplomatic & commercial importance, despite actual agricultural production closer to one-tenth that figure
- Matsumae han - the only han with no official kokudaka
- Hitoyoshi han (Higo province) - 22,000 koku
- Tahara han (Mikawa province) - 12,000 koku
- Edo daimyô hyakke 江戸大名百家. Bessatsu Taiyô 別冊太陽. Spring 1978.
- Roberts, Luke. Performing the Great Peace: Political Space and Open Secrets in Tokugawa Japan. University of Hawaii Press, 2012. p54.