The Random Walk of High Frequency Trading

TL;DR

This paper models high-frequency equity returns by analyzing trade-time and clock-time dynamics, revealing Gaussian trade-time returns and a structured model linking trade arrivals to volatility and market stability.

Contribution

It introduces a novel model combining trade-time Gaussian returns with a Markov-Switching Multifractal Duration process to explain high-frequency return behavior and market stability.

Findings

Trade-time returns are Gaussian at fine scales.

Over-dispersion causes volatility clustering.

Market separation limits systemic volatility.

Abstract

This paper builds a model of high-frequency equity returns by separately modeling the dynamics of trade-time returns and trade arrivals. Our main contributions are threefold. First, we characterize the distributional behavior of high-frequency asset returns both in ordinary clock time and in trade time. We show that when controlling for pre-scheduled market news events, trade-time returns of the highly liquid near-month E-mini S&P 500 futures contract are well characterized by a Gaussian distribution at very fine time scales. Second, we develop a structured and parsimonious model of clock-time returns by subordinating a trade-time Gaussian distribution with a trade arrival process that is associated with a modified Markov-Switching Multifractal Duration (MSMD) model. This model provides an excellent characterization of high-frequency inter-trade durations. Over-dispersion in this distribution of inter-trade durations leads to leptokurtosis and volatility clustering in clock-time returns, even when trade-time returns are Gaussian. Finally, we use our model to extrapolate the empirical relationship between trade rate and volatility in an effort to understand conditions of market failure. Our model suggests that the 1,200 km physical separation of financial markets in Chicago and New York/New Jersey provides a natural ceiling on systemic volatility and may contribute to market stability during periods of extremely heavy trading.