Saver types : an evolutionary-adaptive approach

We set up an agent-based macromodel focusing on consumption-saving without the assumption of utility maximization, but preserving certain "rational" aspects of human choice based on the idea of ecological rationality Todd et al. (2012). In this framework we address the classical problem of the efficiency of long-run capital accumulation. Three qualitatively different saving strategies are defined: 1. buffer stock saving (prudent and forward looking), 2. permanent income saving (forward looking without prudence), and 3. myopic saving (caring only about immediate consumption, and saving accidentally). In the model these types (that have subtypes depending on continuous parameters) may coexist, and we explore their respective survival chances by conducting simulations. It is found that prudent saving behavior becomes prevalent when the selection pressure is very high, but an economy comprising only prudent households tends to accumulate capital in excess of what is implied by the Golden Rule. As selection pressure is reduced, myopic consumers appear, and under very low selection pressure the distribution of the main saver types becomes almost random. A seemingly puzzling fact emerges: the economy gets close to the Golden Rule of capital accumulation via endogenous selection of subtypes in a way that can be interpreted as "perverse exploitation", i.e. the exploitation of the rich by the poor. In other words, lowering the intensity of evolutionary forces, that results in more diversity in saver types, may be socially beneficial. Crickets may be useful for society as a whole, including prudent and cautious ants.