SEMAINE D'ETUDE SUR LE ROLE DE L’ANALYSE ECONOMETRIOUE ETC.

i

of them is properly represented in our accounting system. Some
‘thoughts on this subiect are given in F&! "561.

bY Relationships. The general nature of the relationships
connecting production, consumption, accumulation and foreign
rade was defined long ago by the great economists of the
second half of the nineteenth century, such as JEvoNs, WALRAS,
MARSHALL and PARETO. Their contribution was, precisely, to
formulate an economy as a system. These general ideas were
set out fully and explicitly by BowLEY [4], who remarked in
his introduction that « there seems to be no book in existence,
at least in English, that presents in a coherent form the mathematical
 treatment of the theory of political economy which has
Seen developed during the past eighty years or more. » This
was said in 1924.
But these general ideas provide no more than a guide. In
trying to formulate the economy as a system, the great writers
of the past naturally made many simplifying assumptions. For
example, in the theory of consumers’ behaviour, they assumed
that an individual tries to maximise the utility of his consumption
 subject to a fixed set of prices and a budget constraint.
In this theory individual preferences are assumed to be fixed.
[f, like these writers, we are concerned with formulating economic
 relationships in a general way, this is a legitimate assumption
 which leaves us free to concentrate on the constrainedmaximum
 problem whose solution is the outcome of the theory.
But if we are interested in empirical demand analysis we
cannot make such an assumption since we know that individual
oreferences change, partly because the circumstances of the
individual change with age and partly because, with time,
new commodities appear and social attitudes and fashions
change. Thus is studying the pattern of consumers’ expenliture
 over time, it may be more important to find a way of
allowing for changes in preferences than to have a very sophisticated
 means of allowing for responses to income and prices

Stone - pag. o