and recourse to this creature raises the basic
problem which I have mentioned and which was encountered on the route
to the place where general equilibrium has found itself: the problem of
aggregation. In fact, we know, as I have already pointed out, that in general,
there is no simple relation between individual and aggregate behaviour,
and to assume that behaviour at one level can be assimilated to that
at the other is simply erroneous. Just to give an elementary example, from
the standard assumptions on individuals, it follows that each of their
demand for goods satisfy the ‘Weak Axiom of Revealed Preference’
(WARP); that is, if in some situation, an individual chooses alternative
‘x’ when he could have chosen ‘y’ he will never choose ‘y’ when ‘x’ is
available. But, unfortunately, if we sum the demands of two individuals,
both of whom satisfy WARP, their aggregate demand may not satisfy it.
Thus even well-behaved individuals do not, in sum, necessarily have well behaved
demands