Jonathan E. Leightner   Tomoo Inoue   
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH 178(3) 819-840 2007年5月 [査読有り]
Omitted variables that interact with included independent variables change the vertical placement of observations. Thus, by projecting the data to an output oriented VRS DEA frontier, the influence of omitted variables can be eliminated. After thi...
JOURNAL OF RISK AND INSURANCE 71(3) 501-530 2004年9月 [査読有り]
This article tests economies of scale and economies of scope for the property-casualty insurance companies in Japan. We fit a composite cost function to a set of Japanese firms over the period from 1980 to 1995 and employ an error components model...