Concentration‐Based Merger Tests and Vertical Market Structure
推导出一个衡量多垂直环节市场集中度的指标，即垂直赫芬达尔指数，用于评估垂直并购的竞争效应，为反垄断执法提供量化检验标准。
In this article I derive a concentration measure for markets with multiple vertical segments. I derive the measure using a model of vertical contracting in which upstream and downstream firms bargain bilaterally and may be integrated. The resulting vertical Hirschman‐Herfindahl index provides a measure of the degree of distortion in the vertical chain as a result of both the horizontal concentration in a segment and the degree of its vertical integration. This measure distinguishes between the differing competitive impacts of upstream and downstream competition, establishes the relative size of integrated firms in each segment, and provides a quantitative threshold test for vertical mergers.