The Components of the Bid-Ask Spread: The case of the Athens Stock Exchange

Abstract

We analyze the components of the bid-ask spread in the Athens Stock Exchange (ASE), which was recently characterized as a developed market. For 18 large and 13 medium capitalization stocks, we estimate the adverse selection and the order handling component of the spreads as well as the probability of a trade continuation on the same side of either the bid or the ask price, using the Madhavan et al. (1997) model. We extend it by incorporating the traded volume and we find that the adverse selection component exhibits U-shape patterns, while the cost component pattern depends on the stock price. For high priced stocks, the usual U-shape applies, while for low-priced ones, it is an increasing function of time, mainly due to the different magnitude of the order handling spread component. Our analysis shows that the order handling component dominates inventory effects, particularly in the first and last half hour of the trading day and hence we observe economies of scale in trading. Furthermore, the expected price change is higher in the low capitalization stocks, while the most liquid stocks are the high priced ones. Moreover, by estimating the Madhavan et al. (1997) model for two distinct periods we explain why there are differences in the components of the bid-ask spread.