In the Dixit-Stiglitz model of monopolistic competition the effects of
individual pricing decisions on the aggregate price index are neglected.
This paper studies the implications of this approximation in terms of the
efficiency of macroeconomic equilibria. We show that allowing for the
price-index effect, makes the degree of inefficiency positively correlated
with the number of agents; it also reduces the scope for New Keynesian
outcomes, such as price rigidity and multiple equilibria.