The 1940s saw the reconciliation of mathematical wartime techniques with social scientific theorizing. This chapter examines how the economy was depicted as a huge optimization problem that would soon be solvable by electronic computers. Investigating input–output analysis as it was done at the Harvard Economic Research Project (HERP) under the directorship of Wassily Leontief illustrates the difficulties of making an economic abstraction work in measurement practice. Chapter 3 draws a trajectory to the Conference of Activity Analysis of 1949, where mathematical economists combined techniques of linear programming with what they saw as conventional economics. The move from planning tools to devices for theoretical speculation came along with a shift in modeling philosophies and notions of realism. Focusing entirely on mathematical formalisms and abandoning the concern with measurement brought about the main research object of the economics profession in the subsequent years: The economy as a flexible and efficient system of production in the form of a system of simultaneous equations. This was the economy that provided the primary point of reference for Solow’s model.

The introductory chapter recaps the genesis of the field of input–output or interindustry analysis as a widely utilized framework to analyze the interdependence of industries in an economy. The introduction chronicles how the input–output framework, conceived originally by Wassily Leontief in the 1930s, has matured over the last seven decades to become a key component of many types of economic analysis and one of the most widely applied methods in economics. This book presents the framework set forth by Leontief and explores the many extensions that have been developed, and the introduction concludes by summarizing the key features of the succeeding chapters, appendices, and related online resources chronicling those developments.

The chapter puts the orignal Cobb–Douglas paper in the context of Douglas’s previous research and the theoretical frameworks and empirical practices employed by economists in the 1920s. Douglas’s early research with the time series version of the regression is described. During this period, Douglas linked his procedure to the marginal productivity theory of distribution, and presented his research as part of a broader effort to build a quantitative account of economic activity on the “valuable theoretical scaffolding” of neoclassical theory. Several friendly critics saw Douglas’s research program as complementary to their own neoclassical-econometric program, but judged Douglas's methods and results based on what they revealed about the characteristics of firm-level production functions. This issue was never crucial for Douglas, who considered an aggregate production function to be an important theoretical entity worth estimating. However, Douglas regarded these economists as potential allies in his effort to promote his new research technique. It was they who had first labeled the relationship that Douglas was attempting to estimate a “production function”, and after 1935 Douglas adopted this label.