debate that continues within and across three fields of inquiry: strategy (McGahan and Porter, 1997;Rumelt, 1991), industrial organization economics (IO) (Schmalensee, 1989), and organizational ecology (OE) (Barnett and Freeman, 1997).The debate has endured in part because the three field's (strategy, IO, and OE) theories, concepts, and measures are calibrated using different units of analyses (firm, industry, and population). We bridge these differences by using an ecological lens to model the performance effects of horizontal mergers at the product-market (resource niche) level. Our core thesis is that firm effects matter: some of the products involved in a horizontal merger will attain and sustain an increase in performance from their premerger level in excess of that explained by industry and population-level effects. Our study identifies three

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Although practiced widely in management education, grading of student participation in class discussions has been criticized by researchers: The instructor simultaneously adopts two incompatible tasks of facilitating class discussion and evaluating student participation; students play for points instead of focusing on learning; and common, instructor-based grading schemes do not motivate all students equally. This article proposes a grading system that addresses these three concerns. The proposed system gives students peer feedback within the domain of participation in class discussion enabling instructors to focus on creating learning opportunities in the classroom. The proposed grading system, with interrater reliability exceeding .80, can easily be modified by individual instructors to suit their teaching styles.