Decision-rule cascades and the dynamics of speculative bubbles

We combine Minsky’s financial fragility analysis, behavioural analysis of decision rules and the evolutionary economics of rule trajectories to provide an empirically grounded and computationally tractable theory of the complex evolutionary dynamics of speculative financial upswings. The behavioural dynamics of asset bubbles can be conceptualized as the joint consequence of the adoption and diffusion process of new investment decision rules coupled with the degradation of those rules as they pass from a few expert investors to larger population of amateurs. We illustrate this using data covering the recent Brisbane property market bubble (1999–2003) and show how it is consistent with the existence of such cascading decision rules. We then explain how multi-agent simulation methods can be used for modelling decision rule cascades.