The Herfindahl neutral point: A firm‐level threshold for managing market concentration with evidence from US hog packing
从并购审查常用的集中度指数中推导出一个企业层面的阈值（赫芬达尔中性点），低于该阈值的企业扩张会降低市场集中度，高于则增加。基于2004-2024年美国生猪屠宰数据，发现2016年集中度飙升源于接近阈值的企业并购，而后续下降源于中型企业扩张。该框架仅需市场份额和基准集中度指数。
Abstract This paper derives a firm‐level threshold, the Herfindahl Neutral Point, from the standard concentration index used in merger review. At this threshold, a marginal expansion leaves the index unchanged. Firms below the threshold reduce concentration when they expand; firms above it increase concentration. We derive exact formulas for discrete capacity additions and define bridging amounts that measure how far each firm sits from the threshold. Applying this framework to monthly federally inspected hog slaughter data from 2004 to 2024, we show that the sharp rise in concentration in 2016 is driven by acquisitions at firms that were near the threshold and then crossed it, while the subsequent partial decline reflects sustained growth among mid‐tier packers operating below it. The 2015 acquisition of Cargill's pork business illustrates how bridging amounts organize merger analysis within a standard concentration screen. Reallocating the $34.7 million in federal capacity grants awarded to hog‐sector processors under a targeting rule based on this threshold lowers the 2024 national hog packing Herfindahl–Hirschman Index by about 147 points relative to the pre‐award baseline. The framework requires only market shares and the baseline concentration index.