A: The analysis of "market structure-enterprise behavior-economic performance" is the main contribution of Harvard School. Among them, the causal relationship between structure, behavior and performance occupies the main position, that is, market structure determines enterprise behavior, and enterprise behavior determines the market performance of economic operation. Therefore, from the perspective of improving market performance, the most important thing is to adjust and directly improve the unreasonable market structure through public policies in order to obtain ideal market performance.