Decomposing Bjurek Productivity Indexes into Explanatory Factors

Caves, Christensen, Diewert introduced Malmquist output, input and productivity indexes into production theory in a systematic way. This paper revisits the debate on how to decompose Bjurek's concept of a Malmquist productivity index into explanatory factors, with a focus on extracting technical progress, technical efficiency change, and returns to scale components. In order to define these components, a reference technology is required. The paper does not make any convexity assumptions on the reference technology but instead follows the example of Tulkens and his coauthors in assuming that the reference technology satisfies free disposability assumptions. The existence and properties of the underlying distance functions of the productivity decomposition are proven under relatively unrestrictive assumptions. The paper provides for the first time a theoretical justification for the geometric average form of the Bjurek productivity index