Scientific advance, so rapid over the past century
 and a half, has increasingly become the strategic
 determinant of the influence of natural resources
 on the trend of social welfare over time. In
 advanced countries, it has freed man of the need
 to be concerned about diminishing returns (26)

 But an escape from diminishing returns, one of

the principal "laws" of political economy, is far from

certain. Although during the past century in the United

States labor and capital costs decreased per unit of

minerals output and minerals prices have remained

relatively firm, the same situation need not hold true

in the future. In fact, metals prices have begun to

rise of late, although it is too early to determine

whether or not such price increases represent a trend.

 One should remember that metals can be obtained

under current conditions at relatively low cost only

because they are found in relatively high concentrations.

While on the average the earth's crust contains only

about 0.01 percent copper and about 5 percent iron, these

metals currently are mined at concentrations considerably

higher, about 0.6 percent in the case of copper and 50

percent in the case of iron. Since concentrations of

metals or other minerals in certain locations represent

anomolous situations, one might suspect large concen-

trations of high-grade ore to be very rare,

concentrations of lower grade ores less rare and so on,


 26Barnett and Morse, Scarcity and Growth, p. 261.