Richard Goodwin was an American economist, a self-described ‘wayward Marxist’ who taught at Harvard and Cambridge as well as at Siena. One of his best-known papers was a mathematical model of Marx’s description in *Capital *of the macroeconomic relationship between wages, growth and unemployment, which generates an endogenous growth cycle: that is, it shows how economies can grow over time with fluctuations of output, employment and the other variables in the model generated from within the system, rather than being dependent on external or exogenous ‘shocks’.

Goodwin’s growth cycle model famously draws on the Lotka-Volterra predator-prey model from biology. This describes the dynamics of two interrelated animal populations: the predator and the prey. Starting from, say, a relatively large initial level of the predator population, this could cause the numbers of prey to fall as they are consumed. As the numbers of prey diminish, there is less food for the predator population, whose numbers also then begin to diminish. Falling numbers of the predator population then allow the prey numbers to recover so that they begin to provide a more plentiful food supply for the predators, whose numbers then begin to rise once again. This generates two interdependent fluctuating population cycles, which are not reliant on external or exogenous factors or shocks. Continue reading