We compare the relative magnitudes of the components of the bid‐ask spread for New York Stock Exchange (NYSE)/American Stock Exchange (AMEX) stocks to those of National Association of Securities Dealers Automated Quotations (NASDAQ)/National Market System (NMS) stocks. We find that the order‐processing cost component is smaller, and the adverse selection component is greater on the NYSE/AMEX trading systems than on the NASDAQ/NMS system. The inventory holding component is also greater for exchange‐traded stocks than for NASDAQ/NMS stocks, but this may be attributable to differences in the characteristics of the firms whose stocks trade on the respective systems.

We investigate the relation between earnings predictability, information asymmetry and the behavior of the adverse selection cost component of the bid‐ask spread around quarterly earnings announcements for NASDAQ firms. While we find an increase in the adverse selection component of the bid‐ask spread on the day of and the day prior to quarterly earnings announcements for firms with less predictable earnings, we find no evidence of such changes for firms with more predictable earnings. During a non‐announcement period, we find that firms with relatively less predictable earnings have consistently higher total bid‐ask spreads than firms with more predictable earnings. This finding suggests that firms with relatively less predictable earnings have a higher cost of equity capital than comparable firms with more predictable earning streams, ceteris paribus. Hence, earnings predictability may be a legitimate concern of managers who wish to minimize their cost of equity capital at least as it pertains to bid‐ask spreads.