ABSTRACT
Breaking down an intricate quantitative system with many variables into several simpler relationships—each involving fewer variables—is a standard analytical procedure. Let us consider, for example, the process of steel production. The final output depends here on a very great number of different inputs. If one goes back far enough, these will comprise the quantities of various kinds of labor, machinery, explosives, and other auxiliary materials used in extraction of coal; they will also include a not less heterogeneous collection of cost factors of the iron-mining industry. To be complete this list should contain as well a long array of tools, labor skills, and materials used directly in the operation and maintenance of blast furnaces and open-hearth units.
