In the middle of the 11th century, ikkoku heikin-yaku (taxes and labor uniformly imposed on shoen [manor in the medieval Japan] and kokugaryo [provincial land] in a province) was frequently imposed across the country as extraordinary taxation to build an inner court of the Imperial Court.
11世紀半ばになると、朝廷の内裏造営などを目的とした臨時課税を目的に全国に一国平均役を課すことがしばしば行われるようになった。