This work may be best described as an attempt to construct a of the United States. - Wassily Leontief

The total number of multiplications involved in the practical solution of our problem exceeds 450,000. This task alone would mean a two-year job, at 120 multiplications per hour. Fortunately, the recent invention of the Simultaneous Calculator by Professor Wilbur of the Massachusetts Institute of Technology has made it possible to perform all the necessary computations in a small fraction of the time they otherwise would have required. This apparatus solves nearly automatically a system of nine simultaneous linear equations.

By the time it comes to interpretation of the substantive conclusions, the assumptions on which the model has been based are easily forgotten. But it is precisely the empirical validity of these assumptions on which the usefulness of the entire exercise depends... A natural Darwinian feedback operating through selection of academic personnel contributes greatly to the perpetuation of this state of affairs.

The statistical study presented in the following pages may be best defined as an attempt to construct, on the basis of available statistical materials, a of the United States for 1919 and 1929. One hundred and fifty years ago, when Quesnay first published his famous scheme, his contemporaries and disciples acclaimed it as the greatest discovery since Newton’s laws. The idea of general interdepence among the various part of the economic system has become by now the very foundation of economic analysis. Yet, when it comes to the practical application of this theoretical tool, modern economists must rely exactly as Quesnay did upon fictitious numerical examples.