On the Misuse of the Profits-Sales Ratio to Infer Monopoly Power
指出，在结构-行为-绩效范式中，用利润-销售比率作为勒纳指数的替代指标存在严重偏差，除非正确考虑资本估值和资本成本处理，否则该比率无法准确衡量垄断势力。
A large literature tests the structure-conduct-performance paradigm by regressions which use the profits-sales ratio as the dependent variable.That ratio is used because, under constant returns, it is generally supposed that profits/sales equals the Lerner measure of monopoly power.Profits/sales ratios are also used to make inferences about monopoly power for individual firms.This paper shows, however, that unless proper account is taken of the valuation of capital and the treatment of capital costs, profits/sales will be a very substantially inaccurate surrogate for the Lerner measure.Such proper account requires Hotelling valuation of capital goods which real firms do not use.