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.