Direct Estimation of Synergy: A New Approach to the Diversity-Performance Debate
直接估计美国制药企业1960-1980年间不同业务组合的协同效应，发现生产相关性（如药品与化学品）并不必然带来协同，且协同模式随行业生命周期变化。
This study examines the linkages between relatedness and synergy in the context of diversification among U.S. pharmaceutical firms for the period 1960–1980. Rather than assume (as in the entropy, Herfindahl and concentric indices of diversification) that the levels of synergy generated by different related combinations of business units are identical, we estimate synergy directly using a modified version of the concentric index. In addition to estimating synergy using capital market performance of the firm as a whole, we examine the effects of nondrug diversification on the innovative productivity of firms' pharmaceutical divisions alone. Our two main findings are that production relatedness, such as that between drugs and chemicals, in fact did not imply synergy over the period of our study; and that the patterns of synergy for different types of relatedness shifted over time with the industry life cycle.