680 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA -
>;
to produce it eventually, although in the meantime it may
run into various difficulties.
These have undoubtedly been important steps in the deve-
lopment of dynamic economic analysis. There is in fact
nothing in them, which is incompatible with the dynamic mo-
del developed in the present work. We may say that they
represent a concentration of powerful analytical tools on one
particular case: the case of constant returns to scale and no
technical progress. Unfortunately, this particular case, elegant
and exciting though it may be from a purely analytical point
of view, has, on empirical ground, very little practical re-
levance.
In the foregoing discussion of the relation between the
input-output static model and our vertically-integrated dyna-
mic model, there is a point to which all the voN NEUMANN
types of models can be traced back. It has been said in
section 3 that when, from an analysis of a system at a given
point of time, we pass over to considering movements through
time, the inverse matrix of the technical coefficients, which
provides the analytical bridge between the two models, breaks
down, because of technical change. All the voN NEUMANN
types of models have been an attempt to resist — for analytical
purposes — this hard fact; and to maintain that analytical
bridge through time by assumption, if nothing else. But such
an assumption, convenient though it is mathematically, has
clearly nothing to do with the real world. It means omitting
deliberately what has been singled out, in our previous ana-
lysis, as the basic force responsible for the dynamism of a
modern society, namely the process of learning which goes
on, both on the technical and the demand side. In point of
fact, nne may even question the type of dynamics these models
have adopted, which has meant introducing time into a static
framework with the careful preoccupation of not affecting the
static framework itself. In a sense, time has no importance
in these models. since the features of the economic svstem
‘10] Pasinetti - pag. 110
