Methoden vergleichen

	Herfindahl Diversification Index	Merger and Acquisition Performance Event Study
Fachgebiet	Strategisches Management	Strategisches Management
Familie	Process / pipeline	Process / pipeline
Entstehungsjahr	1979	2001
Urheber	Alexis Jacquemin & Charles Berry; Krishna Palepu	Gregor Andrade, Mark Mitchell & Erik Stafford; David King, Dan Dalton, Catherine Daily & Jeffrey Covin
Typ	Continuous index of corporate diversification with related/unrelated decomposition	Event-study pipeline for the wealth effects of merger and acquisition announcements
Wegweisende Quelle	Jacquemin, A. P., & Berry, C. H. (1979). Entropy measure of diversification and corporate growth. The Journal of Industrial Economics, 27(4), 359-369.	Andrade, G., Mitchell, M., & Stafford, E. (2001). New evidence and perspectives on mergers. Journal of Economic Perspectives, 15(2), 103-120.
Aliasnamen	Entropy Measure of Diversification, Corporate Diversification Index, Jacquemin-Berry Entropy Index, Berry-Herfindahl Diversification Measure	M&A Abnormal Returns Analysis, Acquisition Announcement Event Study, Acquirer-Target Wealth Effects Analysis, Deal Announcement CAR Analysis
Verwandt	3	3
Zusammenfassung	The Herfindahl diversification index and its entropy cousin turn a firm's spread across businesses into a single continuous number, with the decisive advantage that the entropy form can be cleanly split into related and unrelated diversification. The Herfindahl-based measure is one minus the sum of squared segment revenue shares; the entropy measure, introduced for diversification by Jacquemin and Berry in 1979, is the share-weighted sum of the logged inverse shares. Jacquemin and Berry's key contribution was showing that total entropy decomposes additively into within-industry-group (related) and between-group (unrelated) components. Palepu's 1985 study applied this entropy decomposition to strategic management, finding that related diversification was associated with superior profit growth and giving the field an objective, replicable alternative to categorical schemes.	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.