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by expenditures for public health, by family allowances, by 
government policies toward family planning, and by general 
cultural and religious attitudes toward the idea of population 
control. In addition, both variables are in part endogenously 
affected by the level of income. 
Both possibilities of partial control raise new conceptual 
problems in formalizing the idea of optimal economic growth. 
In the middle of the scientific explosion, it is hard to assess 
whether technological progress can go on forever, so that also 
its rate can be raised or lowered forever. It is conceivable that 
a higher rate of discovery and invention in the present will 
entail a lower rate of progress at some later time when the fund 
of knowledge usable in production nears completion. Another 
consideration is that technological progress raises transition and 
dislocation difficulties that affect the relative welfare of different 
individuals within the same generation. 
The possibility of influencing population size raises the 
question of the value of population size in itself — as distinct 
from the question of the weight given to numbers in aggregating 
utility over generations, discussed above. It should be noted 
that all utility functions discussed in this paper imply neutrality 
with regard to population size as such. The question is of some 
importance because a different attitude might lead to a different 
balance between the « value of numbers » and the loss of per 
capita income that may result from an increase in the ratio of 
population to land and/or other resources. This problem did 
not come up in the more formal analysis of the preceding section 
because the assumption of constant returns to proportional 
increases in both labor and capital precluded the recognition 
of resource limitations. 
Koobmans - pag. 35