TY  - JOUR
AU  - Dafny,Leemore S.
TI  - Estimation and Identification of Merger Effects: An Application to Hospital Mergers
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 11673
PY  - 2005
Y2  - October 2005
UR  - http://www.nber.org/papers/w11673
L1  - http://www.nber.org/papers/w11673.pdf
N1  - Author contact info:
Leemore Dafny
Department of Management and Strategy
Kellogg School of Management
Northwestern University
2001 Sheridan Road
Evanston, IL  60208-2001
Tel: 847/467-7511
Fax: 847/467-1777
E-Mail: l-dafny@kellogg.northwestern.edu
M2  - featured in NBER digest on 2005-10-03
AB  - Advances in structural demand estimation have substantially improved economists' ability to forecast the impact of mergers. However, these models rely on extensive assumptions about consumer choice and firm objectives, and ultimately observational methods are needed to test their validity. Observational studies, in turn, suffer from selection problems arising from the fact that merging entities differ from non-merging entities in unobserved ways. To obtain an accurate estimate of the effect of consummated mergers, I propose a combination of rival analysis and instrumental variables. By focusing on the effect of a merger on the behavior of rival firms, and instrumenting for these mergers, unbiased estimates of the effect of a merger on market outcomes can be obtained. Using this methodology, I evaluate the impact of independent hospital mergers between 1989 and 1996 on rivals' prices. I find sharp increases in rivals' prices following a merger, with the greatest effect on the closest rivals. The results for this industry are more consistent with predictions from structural models than with prior observational estimates.
ER  -