SEMAINE D'ÉTUDE SUR LE ROLE DE L'ANALYSE ECONOMETRIQUE ETC. 
ta 
luation, which will lead away from what is useful, If you will 
allow me, I will pick out a few expressions in Prof. FISHER's pre- 
sentation, which exemplifies how one may be carried away by the 
words, I put it down while he was talking. He said that Wozn 
has shown that this particular estimate — it was ordinary least 
square if I remember correctly — « retains desirable properties » — 
well, how do you know what is desirable? And, even worse, later 
on in his presentation, Prof. FISHER said — and I also took this down 
— « retain all the desirable properties » — I think he spoke about 
a full information maximum likelyhood or something that approxi 
mated it. It was in this connection that he said « retain all the 
desirable properties n. The immediate question is: « desirable for 
what purpose? » — May I finally give a third example. Professor 
FISHER spoke about using lagged variables as instruments and advis- 
ed against this use for statistical reasons. Now, suppose I am in an 
underdeveloped country. And suppose I am giving advice to a po- 
litician who is up against the problem whether he should go in for 
education on birth control. In an underdeveloped country with a 
very heavy population increase and with all the implications which 
this means from the economic and social viewpoint, the problem is 
important and the politician is pondering very hard the foreseable 
effect; this case pertains, of course, essentially to lagged variables. 
Suppose I come along and say « Well, I must advise against 
such a policy because it would upset certain calculations of mine 
regarding some specific properties of my estimates ». As I see it, 
these properties of my estimates are purposefully irrelevant, In this 
case it is precisely the lag values one would need to explain demo- 
graphic development. 
Finally, if I may just have one minute, Approaching all these 
things from the viewpoint of society at large, extending over time. 
we are accustomed to fall back on time series to a large extent 
Sometimes we may use cross-section studies, but many economists 
and statisticians rely on time series that come from observation of 
what has happened in the past. Such series are, however, irrele- 
vant for a great number of the estimates of the equations that enter 
[6] Fisher - pag. 72