특히 북한의 폐쇄성과 더불어 북한-중국의 무역도 2000년대 중반까지는 미미한 상태였기 때문에 많은 연구가 이루어지지 않았다.
In particular, since North Korea-China trade, along with North Korea's closed nature, was insignificant until the mid-2000s, much research has not been conducted.