In the market where a za obtained an exclusive right to sell their merchandise, at the same time, they attempted to monopolize the market by prohibiting merchants and artisans who did not participated in that za from engaging in trade, and thus they sustained small traders belonging to the za.
その一方で自己の専売を確立した市場では座外の商人・職人の営業を禁止して座衆による独占を図り、座に属する小規模業者の維持に努めた。