In this feverish world of ours, where one wants the economic analyses to produce easily understandable results quickly and at the least possible cost, some of us have fallen into the habit of assuming for simplicity that the hundreds sometimes thousands of variables that enter into the analyses are linked together by very simple relationships. Frequently we even go so far as to assume linear relationships. Only in this way have we been able to feed our problems into the electronic computers and get mechanical answers quickly and at low cost.

R. Frisch (1964), Theory of Production, p. v: Lead paragraph of preface - 1940-60s