Security Bid/Ask Dynamics with Discreteness and Clustering : Simple Strategies for Modeling and Estimation

The short-term movements of a security price reflect the latent efficient price (conditional expectation of terminal value) and also components arising from the trading mechanism itself. Observed bid and ask quotes are but rough signals of these unobserved quantities. The bid and ask quotes in the $/DM market considered here, for example, are discrete, with a tick size that is not trivial relative to the spread. Furthermore, the distribution of these quotes is clustered, with a greater-than-expected incidence of five-tick multiples. This paper suggests a simple framework for handling discrete, clustered quotes. Despite the simplicity of the model, estimation by traditional (likelihood or moment) methods is difficult. As an alternative, the paper implements a Gibbs sampler approach that proves to be quick and effective. This strategy opens the door for the investigation of a broad class of structural microstructure models