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 I92O-I96O 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 AMD IRON IN USB--ADJUSTED FOR
1860-1900 PRODUCTION
(Millions of 1954 Dollars)
Year
Copper
Iron
i960
21,930
27,442
1920
5,706
9,177
1900
1,905
2,429
Source: Tables 23 and 24. Method of
computation explained above.