Eur. Phys. J. B 71, 467-479 (2009)
https://doi.org/10.1140/epjb/e2009-00316-y

Eroding market stability by proliferation of financial instruments

¹ SISSA, Via Beirut 2-4, 34014 Trieste, Italy
² Istituto di Fisica Nucleare, sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy
³ The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34014 Trieste, Italy

Corresponding author: ^a marsili@ictp.trieste.it

Received: 9 December 2008
Revised: 18 July 2009
Published online: 26 September 2009

Abstract

We contrast Arbitrage Pricing Theory (APT), the theoretical basis for the development of financial instruments, with a dynamical picture of an interacting market, in a simple setting. The proliferation of financial instruments apparently provides more means for risk diversification, making the market more efficient and complete. In the simple market of interacting traders discussed here, the proliferation of financial instruments erodes systemic stability and it drives the market to a critical state characterized by large susceptibility, strong fluctuations and enhanced correlations among risks. This suggests that the hypothesis of APT may not be compatible with a stable market dynamics. In this perspective, market stability acquires the properties of a common good, which suggests that appropriate measures should be introduced in derivative markets, to preserve stability.