* For some industries, the Census Bureau prefers to state concentration ratios on the basis of value added by manufacture rather than value...
* For some industries, the Census Bureau prefers to state concentration ratios on the basis of value added by manufacture rather than value of shipments because, according to the Census Bureau, the latter includes a substantial and unmeasurable amount of duplication for those industries. Source: u.S. Department of Commerce, Bureau of the Census, Census of Manufactures, 1972, Concentration Ratios in Manufacturing, MC76(SR)-2, p~ 28. of 4-firm concentration ratios in manufactur ing in 1972. As table 2.16 shows, the weighted average 4-firm concentration in manufactur ing was 40.2 percent for all 453 industr ies for which data were available. There are at least three snortcomings in the Census Bureau's concentration data. First, the omission of foreign competition tends to overstate market concentration in this country. Second, in any country with a l~~ge geographic area such as the United States, concentration ratios derived from the Nation as a whole will frequently understate concentration prevailing in the relevant regional markets. For example, it is frequently argued that the western United States constitutes a separate market. Imports (particularly from Japan) have a considerable influence in the U.S. west coast market. Third,
industr ies and markets may not be coterminous, with an indeterminate effect on concentration. A more detailed examination of concentration is possible from the 5-digit sic product categories. 17/ In 1972 the four largest firms accounted for 58 percent of the ingot and semifinished shapes, 54 percent of the hot rolled sheet and strip, and 59 percent of the hot rolled bars, plates, and structural 17/ Census data on value of shipments and concentration are rëported on two bases: industry and product. Plants are reported in the industry for which the pr imary product accounts for the greatest value of shipments. All shipments for a plant are reported in the same industry under the industry concept. Under the product concept, all shipments of a given product are classified in the industry to which the pr imary product belongs, regardless of where the item is produced.
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