In the earliest years, merchants peddling from city to city had taken a role in so-called trade, so it is considered to be developed into massive trade routes including overseas trades after the routes were organized and connected each other according to the development of transport technologies.
いわゆる貿易も、当初の頃はこういった行商で都市間を巡回していた商人らが担っており、これが交通・輸送技術の発達にも従い、より組織化され相互連結されて海外貿易などの極大な交易網に発展していったと考えられる。