Market Microstructure
The study of how trading mechanisms and market design affect price formation and transaction costs.
What is Market Microstructure?
Market microstructure is a branch of finance that examines how trading mechanisms, information flows, and market design affect the process of price discovery and the costs of transacting in financial markets. It analyzes the behavior of market participants — including market makers, institutional traders, and retail investors — and how their interactions shape bid-ask spreads, order flow, liquidity, and short-term price dynamics. Key topics include the role of information asymmetry in trade execution, the impact of high-frequency trading, order book design, and the effect of regulation on trading costs. Market microstructure research directly informs exchange design, trading regulation, and best execution standards.
Example
The shift from fractional to decimal pricing on U.S. exchanges in 2001 (decimalization) is a landmark market microstructure event. Reducing the minimum price increment from 1/16 dollar ($0.0625) to $0.01 dramatically narrowed bid-ask spreads — benefiting retail investors who pay less to trade — while also compressing market-maker profitability and spurring the rise of high-frequency trading strategies.
Source: SEC — Report on the Decimalization of U.S. Securities Markets