Module I·Article VI·~3 min read
Market Liquidity: Measurement and Significance
Structure of Financial Markets and Infrastructure
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Market liquidity: a critical factor for investors
Liquidity is one of the most important characteristics of a financial market, defining the ability of participants to quickly buy and sell assets without significantly affecting the price. Understanding liquidity is critically important for choosing instruments, evaluating transaction costs, and managing execution risks.
Measurement of liquidity
Liquidity is a multidimensional concept that cannot be reduced to a single indicator. The main measurements include:
- Tightness — measured by the bid-ask spread, the difference between the best purchase and sale prices. A narrow spread indicates low costs for immediate execution. For liquid shares of large companies, the spread may be fractions of a percent; for illiquid ones — several percent.
- Depth — the volume of orders in the order book at different price levels. A deep market allows execution of large orders without significant price shifts. Measured by the volume at the best prices and the aggregate volume within a certain deviation from the mid-price.
- Resiliency — the speed of liquidity restoration after large trades or shocks. A resilient market quickly absorbs trading imbalances and returns to normal condition.
- Immediacy — the time required to execute an order of a given size. For small orders in liquid markets — milliseconds. For large institutional orders — hours or days.
Determinants of liquidity
Market structure affects liquidity. Centralized markets with a unified order book are usually more liquid than fragmented ones. The presence of market makers with quoting obligations supports liquidity during stress periods.
Asset characteristics determine the basic level of liquidity. Liquidity is higher for: large issuers (more investors follow the stock), assets with high free-float, standardized instruments, assets with transparent pricing.
Market conditions influence liquidity cyclically. In periods of low volatility, liquidity is usually high. In crises, liquidity can evaporate — market makers reduce positions, investors shift to a wait-and-see mode.
Measuring liquidity in practice
Bid-ask spread is the most accessible metric.
- Quoted spread measures the difference between quoted prices.
- Effective spread considers actual execution prices, which may differ from quotes due to slippage.
The Amihud illiquidity ratio measures the impact of volume on price: the average ratio of absolute return to trading volume. High values indicate illiquidity — a small volume causes significant price movement.
Roll measure evaluates the effective spread based on autocovariance of returns. Negative autocovariance arises due to bounce between bid and ask.
Liquidity and investment decisions
Illiquidity premium — illiquid assets must offer higher expected returns to compensate for the costs and risks of illiquidity. Empirical studies confirm the existence of such a premium.
Transaction costs must be considered when evaluating strategies. A high-turnover strategy may be profitable on paper but unprofitable after accounting for spreads and market impact.
Liquidity risk — the possibility that liquidity worsens at the moment when assets need to be sold. This is especially relevant for leveraged strategies, which may be forced to liquidate positions during margin calls.
Liquidity as systemic risk
The events of 2008 demonstrated the systemic nature of liquidity risk. When many participants simultaneously try to sell assets, liquidity disappears precisely when it is most needed. Fire sales exacerbate price declines, creating a vicious circle.
Regulators after the crisis have strengthened requirements for liquidity risk management. The Liquidity Coverage Ratio (LCR) requires banks to hold enough liquid assets to cover outflows under a stress scenario.
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