201
approximately the same throughout the period, rates of
growth in the stock of metals in use would not be greatly
affected.
While additions to metals in use have been greatly
influenced by economic conditions prevailing in any given
year, so that rates of consumption have varied consider-
ably not only by year but also by decade, the stock of
metals in use appears to have increased at an exponential
rate during the period 1920-1960 taken as a whole. An
exponential rate of growth in gross national product
would seem to have been matched by an exponential rate
of increase in metals in use.
TABLE 26
COPPER AND IRON IN USE--ADJUSTED FOR
1860-1900 PRODUCTION
(Millions of 1954 Dollars)
Year Copper Iron
1960 21,930 27,442
1920 5,706 9,177
1900 1,905 2,429
Source: Tables 23 and 24. Method of
computation explained above.