I. The basic model, 217. — II. Multiplicative demand curves and steady growth expectations, 222. — III. Equilibrium solutions, 226. — IV. Nonconstant returns to scale, 230. — V. Rule-of-thumb decision making and steady growth solutions, 232. — VI. Summary and conclusions, 234.

Economists have recently grown interested in doing research on research or R & D, as it is called in industrial circles. Several studies have tested Schumpeter's hoary hypothesis that large firms are responsible for most industrial inventive activity.1 Few of these studies, however, suggest why this hypothesis is apparently valid for some industries and not for others. And statistical studies going beyond this question, to try to relate R & D expenditures to firm profit expectations and the avail-ability of funds as in other investment decisions, are rare (Mansfield, 1964; Mueller, 1967). This paper reports the results of an empirical investigation into the determinants of research expenditures in three industries-drugs, chemicals, and petroleum refining. These industries have three advantages for such a study: (1) they are among the leaders in total R & D expenditures; (2) most activity is concentrated in an appreciable number of large or moderately large firms; and (3) government support of research work is

A computer simulation model in the tradition of evolutionary models of technical change is developed in this paper. It focuses on R&D competition in new product introductions and is based on data for the U. S. pharmaceutical industry during the 1970s. The sensitivity of innovation levels to the rate of generic competition, regulatory review time, and patent life is examined in the computer simulation experiments. These factors are found to have significant long-run effects on industry structure and innovation levels.

IN a recent paper investigating the efficiency of earnings retentions, Baumol, Heim, Malkiel and Quandt (1970) (hereafter BHMQ) estimate the rate of return on earnings retentions, debt and new equity for a large cross section of firms. They find new equity earns considerably higher returns than the ploughback of profit and depreciation, with the returns on new debt falling between. BHMQ do not explain these striking results, beyond suggesting a lack of market discipline on the reinvestment of internal funds. In their concluding remarks, they pose a number of open questions for future research and analysis

T HIS study investigates within a comrnon analytical framework the determinants of firm expenditures o;n capital investment, research and development and dividends. Its two basic objectives relative to past work are: first, to probe more deeply into the forces determining these outlays by taking into account the interdependencies among them,' and second, to provide a framework for evaluating alternative assumptions regarding firm motivation. A firm maximizing stockholder objectives will exhibit different behavior in its expenditure decisions from one pursuing managerial goals. Consequently, two main variants of a model of firm expenditures, based on these rival concepts of motivation, are developed and tested.