This chapter presents speculation regarding factors that contributed to the success of the Cobb–Douglas regression. I discuss in particular four factors that helped facilitate the widespread adoption of the regression approach to production function estimation. (i) Douglas’s decision to link his procedure to fundamental concepts of the neoclassical approach to economics, which was destined to grow in influence over the course of the twentieth century. (ii) the flexibility and adaptability of the technique. (iii) Douglas’s rhetoric of persuasion, and (iv) the emergence of prominent advocates for the technique, such as Earl Heady and Zvi Griliches who communicated, by words and example, the attitude that despite its weaknesses, the technique was potentially very valuable, that the best way to realize that potential was to continue using the technique while working to address the weaknesses, and that even while this process of improvement was going on, the technique was still able to contribute to knowledge. The question of why such allies emerge is explored.

This chapter describes a process in which a number of long-standing hypotheses about sources of economic growth came to be represented as a series of modifications to Solow’s basic neoclassical production function, which in turn led to attempts to test empirically these hypotheses using production function regressions. Particular attention is given to two empirical research programs that made use of variants of Douglas’s regression procedure: the literature on “embodied technical change” initiated by Robert Solow, and Zvi Griliches’s work measuring the causes of economic growth, both of which emerged in the late 1950s and early 60s. Griliches and Solow proposed empirically tractable ways of testing various hypotheses about causes of economic growth. Their proposals were attractive in part because they made use of an empirical procedure, production function estimation, that involved statistical methods that were coming to be the foundation of graduate training in econometrics, and because they were expressed in terms of the mathematical neoclassical theory that was becoming central to graduate training in economic theory.

The introduction provides an overview of the book. Although Paul Douglas is the most important person in the story of the Cobb–Douglas regression, the book is not a biography of Douglas, but of his best known and most successful creation. The book covers the period from the mid-1920s, when Douglas was doing the statistical work that led to the first use of the Cobb–Douglas regression, to the late 1960s, when Douglas’s idea had come to be widely accepted by economists, and the CES production function was emerging as the first popular alternative to the Cobb–Douglas function for estimation of production functions. My perspective is mainly that of a historian of the use of statistical analysis in economics, with particular attention given to the challenges faced by empirical researchers, and the roles played by statistical and economic theory in their development of strategies to overcome them. At various point in the book, I reflect on factors that might have helped the production function regression go from an innovative and controversial statistical procedure to a widely accepted general purpose tool in empirical economics.