<論説>慶雲三年輸租折衷法と熟田

Abstract

日本古代の律令国家は、租と呼ばれる一種の土地税を課していた。その課税は、田一段につき二束二把という定額であったが、これが慶雲三年(七〇六)に一束五把に変更される。通説では、この二束二把から一束五把への変更は、税額の実質的変更をほとんど伴わなかったとされ、租は不変と考えられてきた。しかし、この変更は実質的な大幅減税とみるべき措置である。律令国家が大幅減税に踏み切った背景には、斗升制の転換、口分田の穫稲格差、水旱条の不法適用が存在した。口分田は、律令法上、斉一な収穫量を約束された熟田として扱われているが、これはフィクションに過ぎず、実際には多様な耕営状況が存在している。律令国家は、こうした現実をふまえつつ、土地税としての租を定着させようと図ったのである。

The ritsuryō state in ancient Japan imposed a type of land tax called the so 租. Taxation was fixed at two soku 束 two ba 把 (one ba being a sheaf of rice and ten ba constituting one soku) for each tan 段 (a measure of area) of a rice paddy. In the third year of the Keiun era (706), a regulation called the yuso secchūhō 輸租折衷法 was issued (this new law was a compromise between the then-current and the more-ancient tax collection systems). According to the new law, the tax burden was reduced from two soku two ba to one soku five ba. If understood in literal fashion, this law would have reduced the tax burden to two-thirds of the former amount. However, the current scholarly consensus does not accept this interpretation. It is thought that the reduction of the land tax was minimal and there was very little change in reality. That which had changed was not the amount of the tax burden but the standard for the device used to measure the volume for the tax. This change in the norm for measuring volume has been judged as a defeat for the ritsuryō state. The ritsuryō state attempted to decide on a new norm for a measuring device, but as the populace rejected its introduction, and the government ultimately returned to the older device for measuring volume. In this article I prove that a large-scale tax reduction was in fact carried out reducing the tax to seven ba per one tan on the basis of the yuso secchūhō, and explores the background behind this policy. First, I confirm the logic on which the entire law was constructed and reexamine each word used in the law one by one. According to the yuso secchūhō, the ritsuryō state did not regard the small differences resulting from the different standards as a problem. The ritsuryō state problematized yields that were less than those anticipated for each specified area. The tax burden was originally determined by the estimated yield of the paddy fields, but there was a discrepancy between the estimated amount and the actual yield. As a result, the government both reduced the estimated amounts and was under pressure to reduce the land tax itself. The reduction in tax due to the yuso secchūhō must be considered an actual tax reduction rather than a minor reduction due to a change in the norms. The chief reason for the mistaken scholarly consensus lies with the ninthcentury specialists in the law who were involved in organizing and reinterpreting the laws from more than one hundred years earlier. It is thought that the confusion in interpreting the yuso secchūhō was a product of that effort. Behind the promulgation of the yu so secchūhō were the various problems with which the ritsuryō state was burdened during the period of the early 8th century. During this period the ritsuryō state issued a standard device to measure volume through the land. The scholarly consensus has been that this system ended in failure, but it was in fact a success. However, as the uniform standard spread throughout the land, the populace's consciousness of the land tax burden became more acute. Furthermore, the handen shûjuhō 班田収授法 (the system by which paddy fields, which they were to be cultivated, were distributed to all citizens over a certain age) had only recently been successfully implemented on a nationwide scale. As the extent of its implementation spread, it became difficult to provide good-quality paddy fields, and discrepancies in the amount that could be produced by each field arose. As a result, the difference between the estimated yield and the actual yield became more conspicuous, and the situation had to be corrected. Moreover, at this time a system was also introduced to lessen the tax at times of crop failure. This system was to be applied only when the crop failure was due to natural disasters such as drought. However, when the yield was low, it was difficult to distinguish whether the cause had been a natural disaster or whether it was due to low productivity of the land itself. Because the government set the estimated yield for all yusoden 輸租田 (paddy fields covered by the regulation) at the same level, it was not possible to distinguish fields that were originally of low productivity. It became necessary to lower the estimated yields because the land taxes could not be collected from those paddies that showed a large decrease in production. The yuso secchūhō was a law that was highly significant as it reflected the process of how the so became fixed as a land tax.