Gross National Product, in constant prices,

increased approximately four times between 1870 and

190036 while pig iron production increased more than

eight times, and copper production thirty-eight times,7

so that increases in these were much greater than in

GNP. Since 1900 the rate of increase in copper and

iron production has been much lower, 1.4 percent for

copper and 1.8 percent for iron, while GNP has increased

at an average annual rate of 3.1 percent.8 Hence, at

first glance, GNP would appear to have increased much

more rapidly than metals since 1900, and based upon

these figures, the importance of metals to production

would appear to have decreased over time. But the

figures are misleading.

 Reduction in apparent consumption of metals

relative to GNP has been noted by many writers who

have observed that progressively more has been made

from each ton of metal, which is true. But compari-

sons of levels of GNP with annual rates of apparent

consumption have understated the importance of metals

to production in general. Quite simply, the level of

of production for the whole economy in any given year

 36
 Historical Statistics, p. 139, Series F-3.

 7Figures for iron and copper production and
consumption are included in Appendix B and are related
there to changes in GNP.

 38See Appendix B.1, Table 19.