[This article develops and tests a structural model of intraday price formation that embodies public information shocks and microstructure effects. We use the model to analyze intraday patterns in bid-ask spreads, price volatility, transaction costs, and return and quote autocorrelations, and to construct metrics for price discovery and effective trading costs. Information asymmetry and uncertainty over fundamentals decrease over the day, although transaction costs increase. The results help explain the U-shaped pattern in intraday bid-ask spreads and volatility, and are also consistent with the intraday decline in the variance of ask price changes.]

This article develops and tests a structural model of intraday price formation that embodies public information shocks and microstructure effects. We use the model to analyze intraday patterns in bid-ask spreads, price volatility, transaction costs, and return and quote auto-correlations, and to construct metrics for price discovery and effective trading costs. Information asymmetry and uncertainty over fundamentals decrease over the day, although transaction costs increase. The results help explain the U-shaped pattern in intraday bid-ask spreads and volatility, and are also consistent with the intra-day decline in the variance of ask price changes.