Detecting Abnormal Operating Performance: Revisited
比较了五种生成控制样本的方法，发现基于事前绩效水平、变化和市账比匹配的方法最可靠，且控制绩效水平比控制变化更重要。
Firms that undertake corporate events often exhibit atypical financial characteristics, such that future performance might be expected to change even before the event is announced. I investigate five methods for generating control samples in various sampling situations. The results indicate that the methods sometimes produce severely biased test statistics. Overall, the method that generates control firms with similar prior levels and changes of performance and similar market-to-book ratios produces the most reliable test statistics. Furthermore, I find that it is more important to control for levels of performance than for changes in performance and market-to-book ratios.