A digital simulation model of out-of-equilibrium market behaviour: a Keynesian-Sraffian approach

Keynesian economics has devoted particular attention to out of full employment equilibrium phenomena, but the lack of an analytical framework for describing how economic agents interact and organize their production and consumption decisions has made it difficult to establish whether the economic system is self-adjusting at an out-of-full employment equilibrium. One of the purposes of Sraffa's book Production of Commodities by Means of Commodities was to understand the conditions that allow the system to reproduce itself. But how trade takes place remains an open question. For Sraffian economics, the lack of an analytical framework for describing how economic agents interact and organize their production and consumption decisions, has made it difficult to consider out-of-equilibrium behaviour. The present thesis is a first attempt to model Keynes's principle of effective demand with the aid of Sraffian schemes. The notion of effective demand requires the possibility for buyers and sellers to buy and sell thanks to the existence of newly generated or previously accumulated financial purchasing power. Stated differently, the very notion of out-of-equilibrium exchanges may require the emergence of new credit and debt relations. Sraffa's original production schemes have been enriched with algorithmic behavioural functions that describe agent decisions and exchanges of property rights. In the resulting algorithmic model of an economic system (with labour and goods market), decisions of production and consumption are made by a population of algorithmic rational agents (ARAs), divided between producers and workers. The ARAs are characterized by behavioural functions, specific trading rules, and are connected in a network. Exchanges are made by signing virtual contracts that involve the use of financial means. The creation of new financial means of exchange, credit and debt, is endogenous. Production is heterogeneous and conceived as a circular process. The fundamental conclusion is that this digital economic laboratory has generated virtual economies able to converge towards production prices, uniform wage rates but non-uniform profit rates with an unequal distribution. The virtual economies result to be stable and efficient from a technological point of view despite economic policy can improve the performance of the whole economy. The digital economic laboratory is a powerful instrument able to answer different research questions. It represents an answer to the need to develop models able to explore the complexity of out-of-equilibrium behaviour, grounded on bookkeeping principles and computable methods.