SETS, Arbitrage Activity, and Stock Price Dynamics

This paper provides an empirical description of the relationshipbetween the trading system operated by a stockexchange and the transaction costs faced by heterogeneous investors who use the exchange. The recent introduction ofSETS in the London Stock Exchange provides an excellent opportunity to study the impact of an electronic trading systemupon transaction costs and the time taken to carry out a trade. Using the cost-of-carry model of futures prices we estimate(non-linearly) the transaction costs and trade speeds faced by arbitragers who take advantage of mispricing of FTSE100futures contracts relative to the spot prices of the stocks that make up the FTSE100 stock index. We divide the sample periodinto pre-SETS and post-SETS sample periods and conduct a comparative study of arbitrager behaviour under differenttrading systems. The results indicate that there has been a significant reduction in the level of transaction costs faced byarbitragers and in the degree of transaction cost heterogeneity since the introduction of SETS. Finally, generalised impulseresponse functions show that both spot and futures prices adjust more quickly in the post-SETS period.