Market Structure And Bid Ask Spreads

This paper examines the effects of competition and market structure on the bid-ask spreads for stock options traded on the Chicago Board Options Exchange (CBOE) between 1986 and 1997. Options listed on multiple exchanges are found to have narrower spreads than those listed on a single exchange, but the difference is smaller for effective spreads than quoted spreads, and the effect diminishes as option volume increases. Option spreads become wider when a competing exchange delists the option. Options traded under a quot;Designated Primary MarketMakerquot; (DPM) are found to have narrower quoted spreads than those traded in a traditional open outcry crowd. Effective spreads are found to be slightly narrower under the DPM than in the crowd, but only since 1992, and only on low-volume options.