Economic evidence and proof of a collusive agreement. I investigate whether some economic observations may contribute to prove the existence of an illegal collusive agreement. The facts analyzed are: simultaneous increase in prices, price parallelism, market shares stability, price similarity among firms when firms have different costs, price similarity among firms and products when products have different costs, third degree price discrimination. I find that in many cases these observations per se do not allow to discriminate between a collusive and a competitive equilibrium and that further information on costs and demand is needed to obtain a legal proof.
Published in Economia e politica industriale.