Structural Implications of a Class of Flexible Functional Forms for Profit Functions
指出，一类常用的灵活函数形式在表示利润函数时，会对生产技术的结构施加不理想的限制，包括拟同质性等，即使不施加弱可分性也是如此。
In 1973, Diewert proposed the use of various Flexible Functional Forms (FFF) \n for profit functions. Since then, the use of FFF specifications for profit functions \n in empirical production analysis has become increasingly popular (Woodland \n [1977]; Kohli [1978]; Cowing [1978]; Sidhu and Baanante [1981], etc.). A \n number of alternative FFF specifications are available which may seem equally \n plausible. In fact, the choice among FFF for empirical applications is typically \n a purely arbitrary decision. The central problem considered in this paper is \n whether some FFF impose more or less a priori restrictions on the structure of \n production. The purpose of this note is to show that indeed an important class \n of FFF, when used to represent profit functions, impose quite undesirable \n restrictions on the production technology. These restrictions include quasi- \n homotheticity and certain additional separability structures of the underlying \n production technology. A paper by Blackorby, Primont and Russell [1977] \n shed some doubt on the flexibility of FFF when certain separability conditions \n are imposed. It proved that the flexibility of these forms rest indeed on very \n feeble grounds, being extremely sensitive to weak separability restrictions. These \n forms do not provide second order local approximations to an arbitrary weakly \n separable function. What we demonstrate here is that an important family of FFF \n does impose serious structural rigidities on the underlying production structure \n even if weak separability is not imposed. \n We first present a simple taxonomy of flexible functional forms which allows \n us to classify them into two major families according to certain key differences. \n Next, we show that one of these families imposes quasi-homotheticity and certain \n separability conditions on the underlying production technology. In section 3, \n we provide some general comments concerning the implications of these results \n as a potential basis for discriminating among FFF in empirical analysis. We \n end this note with a summary of the major conclusions.