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until the 1950s. Both iron and copper production
series reflect demands made upon domestic resources,
however, regardless of whether the final destination of
metals produced was domestic or foreign.
Steel production increased more rapidly than
pig iron production for the period 1860-1900 because
many of the final uses of iron were being taken over
by steel, e.g., rails. Rates of growth in pig iron
production after 1900 approached growth rates of pig
iron production more closely, but also reflected the
increased importance of scrap as a steel input.
Between 1900 and 1920, the Bessemer process of making
steel was replaced largely by open-hearth processes;
and while the latter process made extensive use of
scrap, the former had not. Data on scrap use are
included in Part 3 of this appendix.