手法を比較

	Diversification-Performance Analysis (Rumelt Categories)	Merger and Acquisition Performance Event Study
分野	経営戦略論	経営戦略論
系統	Process / pipeline	Process / pipeline
提唱年	1974	2001
提唱者	Richard P. Rumelt; Krishna Palepu	Gregor Andrade, Mark Mitchell & Erik Stafford; David King, Dan Dalton, Catherine Daily & Jeffrey Covin
種類	Classification-and-comparison pipeline relating diversification type to firm performance	Event-study pipeline for the wealth effects of merger and acquisition announcements
原典	Rumelt, R. P. (1974). Strategy, Structure, and Economic Performance. Division of Research, Graduate School of Business Administration, Harvard University. ISBN: 9780875841090	Andrade, G., Mitchell, M., & Stafford, E. (2001). New evidence and perspectives on mergers. Journal of Economic Perspectives, 15(2), 103-120.
別名	Rumelt Diversification Category Analysis, Related vs Unrelated Diversification Analysis, Corporate Diversification Strategy Classification, Diversification Strategy-Performance Linkage	M&A Abnormal Returns Analysis, Acquisition Announcement Event Study, Acquirer-Target Wealth Effects Analysis, Deal Announcement CAR Analysis
関連	3	3
概要	Diversification-performance analysis asks whether the kind of diversification a firm pursues — staying focused, expanding into related businesses, or building an unrelated conglomerate — is systematically associated with how well the firm performs. The categorical version originates with Rumelt's 1974 Strategy, Structure, and Economic Performance, which classified diversified firms by specialization and relatedness ratios into single-business, dominant-business, related, and unrelated types and found that related diversifiers tended to outperform unrelated ones. Palepu's 1985 study reframed diversification with the continuous Jacquemin-Berry entropy measure, again finding that related diversification was associated with superior profit growth, and showed how the index approach and Rumelt's categorical method can be combined to gain both objectivity and conceptual richness.	A merger and acquisition event study measures the stock-market reaction to a deal announcement to infer how much value the deal is expected to create or destroy for acquirers and targets. The logic is that in an efficient market the share-price jump around the announcement capitalizes investors' revised expectations of future cash flows attributable to the deal. Andrade, Mitchell and Stafford's 2001 survey distilled the empirical regularities: targets earn large positive abnormal returns, combined acquirer-plus-target returns are modestly positive, while acquirers themselves often earn around zero or slightly negative returns. King, Dalton, Daily and Covin's 2004 meta-analysis confirmed that acquirers, on average, do not gain and pointed to unidentified moderators, motivating cross-sectional models that link abnormal returns to deal and firm characteristics.