does not depend upon the amount of metal produced in

that year, but rather upon the amount of metal already

in use in machinery, buildings, and other equipment.

As such, current levels of production depend more upon

the rate at which meals production has occurred in the

past than upon the rate at which they currently are

being produced. Current levels of metals production

are more important to future levels of general pro-

duction, and hence are related to growth.

 When stocks of metals in use are compared to

GNP, a different picture emerges. While real GNP in

1960 was approximately 7 times as great as it had been

in 1900, stocks of copper in use appear to have been

about 11.5 times as large and iron 11.4 times as large

as they were in 1900. Even after 1920, when metals

markets had become more diverse and metals were going

to uses for which there tended to be a larger value of

product per unit of metal, stocks of metals in use

continued to increase at a rate comparable to that of

GNP. Stocks of copper in use increased at an annual

rate of 3.4 percent and iron at a rate of 2.8 percent,

while GNP increased at an average annual rate of 3.2

percent.40


 39See Appendix B.4, Table 26.

 4oSee Appendix B.4, Figure 3, Figure 5, Table 27.