Nature
Volume 469 Number 7330 pp265-438  20 January 2011
http://www.nature.com/nature/current_issue.html

Perspectives
Systemic risk in banking ecosystems
Andrew G. Haldane &Robert M. May

Abstract
In the run-up to the recent financial crisis, an increasingly elaborate set of financial instruments emerged, intended to optimize returns to individual institutions with seemingly minimal risk. Essentially no attention was given to their possible effects on the stability of the system as a whole. Drawing analogies with the dynamics of ecological food webs and with networks within which infectious diseases spread, we explore the interplay between complexity and stability in deliberately simplified models of financial networks. We suggest some policy lessons that can be drawn from such models, with the explicit aim of minimizing systemic risk.