The Pigou effect is a concept which concerns the economy. It is also known under the name of effect of boxes real.

To answer the pessimistic diagnosis of the " general theory " of Keynes, according to which the Capitalisme is condemned to a durable Chômage because of the insufficiency of the total request, Arthur Cecil Pigou suggested an assumption resting on the idea that the Monnaie is a richness, and allowing to highlight an automatic rebalancing of the total Demande. This assumption amounts admitting that the agents maintain constant the relationship between the actual value of box monetary (M/P) and their requests for Consumer goods and goods of production (C+I). Consequently, if the total Demande (C+I) is insufficient, the general level of the prices will tend to drop, increasing the actual value of box monetary (because their capacity increases), then the agents thus convert to them surplus Monnaie into request for goods the prices will go back to balance, thorough by the increase in total demand. The mechanism of this Pigou effect rests on the idea that the increase in (M/P) increases the richness of the agents, which feeling richer consumes and invests more. The logic of the sequences is the following:

O>D => p => (M/P) + => D+ => P+ where D=C+I

There is thus according to this theory no possibility of prolonged general overproduction.