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PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
cerning public investment, not the effects of empirically observed 
public investment. Incidentally, in my model there will in general 
be included cycles in public investment too. Koopmans has asked 
whether the conclusions about growth depend on the assumption 
of cycles in private investment. The answer is « yes ». 
WoLD 
When reading Professor HAAVELMO’s paper I was struck by 
‘he contrast between the simple and seemingly innocent assumptions 
on the one side, and the rather startling implications and conclu- 
sions on the other, and at the same time it puzzled me that he gives 
little or no comment whether his results can or cannot be reconciled 
with current theories. Somehow I got the feeling that Professor 
HAAvELMO has written his paper with tongue in cheek, and this 
impression was confirmed as I consulted him about his paper one 
of the first days of the Study Week. I should now like to ask 
whether I have understood his intentions correctly, namely that the 
paper illustrates the danger of mixing together the theories of two 
different regimes of economic conditions: on the one hand the serious 
depression around 1930, and the Keynesian theory of measures to 
get rid of the depression, on the other hand the modern theories 
of economic growth? More specifically, is it the point of the paper 
that the Keynesian assumptions are appropriate for a regime of 
unemployment and unused capacity, whereas these same assump- 
tions lead to unrealistic and startling conclusions in a regime of full 
employment and full utilization of capacity? If so, how are the 
hypotheses underlying Professor HAAVELMO’s simple model to be 
sorted out between the two regimes? A clarifying answer to these 
questions would add greatly to the appropriate understanding of 
Professor HAAVELMO’s important model. 
(81 Haavelmo - pag. 24