The aim of this paper, which is part of a broader research project, is to analyse the fluctuations of output in a framework of imperfect competition based on the stylised facts. We conclude that these movements can be originated by supply or demand shocks, or simply by the adjustment of the economy when goods or labor markets are not balanced because of price and wages rigidities. On the other hand, it justifies the Keynesian argument related to government interference in cases where the economy cannot overcome a recessive stage on its own.
