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The rate at which the movement to marginal
deposits progresses depends in turn upon the rate at
which metal in the form of ore is extracted and upon
the extent and richness of the best ore deposits. The
rate at which ore must be extracted depends upon the
rate of goods production and upon the rate at which
scrap metals are reused. An exponential rate of increase
in production (which may require an exponential rate of
increase in new matals demand of the kind experienced
in the past) must certainly press technology even harder,
given finite quantities of available ore concentrations.
It is by no means certain that technology will forever
4
be equal to the task.
Although increased production requires more
material, the relationship between production and mate
rials needs is not precise, nor is it the same for all
materials. In particular, metals do not bear the same
relationship to levels of output as do other materials.
The rates at which fuels are produced and consumed,
for example, reflect rates of current production.
Greater production requires more fuel, and fuel production
is in turn counted as part of total current production.
In contrast, the rates at which structural materials
Interestingly, those who seem to be the most
confident are economists; the least optimistic seem to be
those whose business it is to provide new supplies of
minerals and those who must generate technological
change.