Perfect Competition and the Keynesian Cross:Revisiting Tobin

I look at an exogenous decrease in the desire to save in a two-sector-two-period overlapping generations model, where the consumption good is capital-intensive and the elasticities of substitution in production are "small". It is shown that there is a Keynesian-type multiplier at work, even though the model is a competitive one with full employment (and inelastic labour supply). It is reminiscent of Tobin (1975) who had shown thirty years ago that Keynesian results could be obtained with (short run) Marshallian dynamics (albeit in an ad-hoc model).