Mueller's Profits in the Long Run
评述穆勒关于企业间长期利润差异的研究，通过时间序列模型分析利润动态，并与横截面研究对比，指出并购与破产对实证分析的重要性。
Mueller uses a measure of persistent, or long-run, interfirm differences in profitability, obtained by estimating a separate time-series model for each firm, to reexamine this question. His results are quite different from those obtained from cross sections of annual profit rates, and the differences shed new light on old issues. Moreover, in describing and analyzing the separate profit series, and in comparing the cross sectional with the time-averaged results, Mueller focuses attention on the dynamics of the profit process and the relative importance of the different factors that affect it. As a result, the careful reader will come away from this book with a set of questions that just might lie at the heart of the debate about profitability movements among manufacturing firms and that ought, at least in part, to be analyzable with currently available tools and data. I have divided my review into four sections. First, I outline Mueller's model and consider its relationship to other recent work on profitability differences. Next, I summarize Mueller's empirical results (both the more descriptive time-series results, and the estimates of his model), and then I provide a brief comparison with the results Schmalensee (1985) and Ravenscraft (1983) obtain on the determinants of cross sectional profitability differences. Any ultimate reconciliation of the different findings, and any more detailed analysis of their implications, will require a deeper understanding of the factors causing profitability movements over time. The last section of this review considers the dynamic issues on which Mueller, and his results, focus attention and discusses the models that seem appropriate for analyzing them. It is clear that further empirical work on these issues must make some allowance for mergers and acquisitions on the one hand, and bankruptcies and liquidations on the other. The review concludes by explaining why this is so and by considering how it might be done.