The product innovation process and GDP dynamics

In this paper, we explain GDP dynamics through an analysis of the forces that modify the structure of the economy. These forces are represented by the entry of new firms and product innovations. Our model is inspired by Bak’s sand pile model, and the entry of a new firm or innovation is comparable to dropping a grain of sand in Bak’s model. The resulting model involves the insights of both Keynes and Schumpeter. It could be defined as Keynesian because the aggregate output is demand driven. That said, the model can mainly be labeled as Schumpeterian for several reasons: (i) innovations have a key role, (ii) credit is involved in supporting the innovation process, (iii) innovations partially destroy old industries, and finally (iv) without innovations, the system gradually approaches its stationary state. In this simple model, the change in the number of sectors (products) of the economy is the decisive factor with the following results: (1) the aggregate production has an increasing trend; (2) fluctuations are asymmetric; (3) recessions have a “creative destruction” explanation; (4) “classical” cycles are gradually replaced by “growth” cycles.