To choose a listed company, the data is relatively easy to obtain; Secondly, select enterprises in the same industry, and the data is easy to compare; Finally, try to choose large-scale enterprises, because the data volume is too small and fluctuates greatly, which is difficult to analyze.

A listed company is a kind of joint stock limited company, which refers to a joint stock limited company whose shares are listed and traded on the stock exchange with the approval of the securities management department authorized by the State Council or the State Council. In addition to being approved, certain conditions must be met.