As the article in 769 of "Shoku Nihongi"(Chronicle of Japan Continued) states that an official of Dazai-fu reported 'this city is lively with people and blooming as a trading center. It is the most prosperous place in Japan' to the capital, in the northern Kyushu, the economy using currency was already active.
だが、『続日本紀』769年の記事で大宰府の役人が都に「大宰府言。此府人物殷繁。天下之一都會也。」と報告しているように北部九州では既に通貨経済が活発であった。