SEMAINE D'ÉTUDE SUR LE ROLE DE L'ANALYSE ECONOMETRIOUE ETC.
23C
made in the previous sector may be considered preparatory
remarks to the application of one or the other of these keys.
Clearly there are more possibilities [3]. Mathematically the
simpler key is the one where we assume an imperfect market
and finite elasticities of substitution between the imports from
alternative regions.
10. The preceding sections are a sketch only of a type of
model which may be used as a framework for regional deve-
lopment planning. The vague way in which it has been describ-
ed illustrates the large number of possibilities of adapting any
concrete model to the particular structure of the country it has
to serve. Thus, the number of regions and their frontiers, the
number and nature of sectors and their distribution over re-
gional, national and international sectors may be so chosen as
to approach reality as much as possible. Even so hardly all
the coefficients it contains will be available from statistical
measurement and some of them will have to be chosen rather
arbitrarily. This applies especially to the substitution elastici-
‘ies for the products whose transportation costs cannot be ne-
glected. Probably it also applies to whatever cases of indivisi-
bilities will be introduced.
Even when the model has been established another choice
has to be made: the one of the type of development policy one
wants to analyse. It is necessary to follow the habits developed
in the theory of economic policy and to define the aims and
means of such a policy. The aims may either be chosen as a
set of numerically given targets or as the maximization of some
social welfare function. For regional policy the welfare function
will depend also on regional variables such as income per head
of the various regions and the most common policies usually
imply a reduction of the income differences. Many specifica-
lions are possible. To laymen such criteria as first raising the
income per head of the poorest region and after a certain pro-
portion to the next poorest region has been reached raising the
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Tinbergen - pag.
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