Module I·Article V·~4 min read
Liquidity and Transaction Costs
Structure of Financial Markets and Infrastructure
Turn this article into a podcast
Pick voices, format, length — AI generates the audio
Liquidity of the Market and Trading Costs
Liquidity is a critically important characteristic of financial markets, influencing the cost and efficiency of investing. Understanding the nature of liquidity and transaction costs is necessary for constructing effective investment strategies and assessing their real returns.
Multidimensionality of the Liquidity Concept
Liquidity is the ability to quickly conduct a transaction without significantly affecting the price. This seemingly simple definition conceals complexity: liquidity has several dimensions that do not always correlate with each other.
Tightness is measured by the bid-ask spread. A narrow spread means low transaction costs for an immediate deal. The spread is determined by competition among market makers, asset volatility, information asymmetry, and trading volume.
Depth is the volume of orders available at various price levels. A deep market is capable of absorbing large orders with minimal impact on price. Depth is especially important for institutional investors with large positions.
Resiliency is the market's ability to restore liquidity after shocks. A resilient market quickly returns to normal spreads and depth after large trades or news events.
Immediacy is the ability to execute a transaction immediately. In liquid markets, there is almost always a counterparty for the deal; in illiquid markets, one has to wait or make a substantial price concession.
Measurement of Liquidity
Practical liquidity metrics include: quoted spread—the difference between the best bid and ask; effective spread—twice the difference between the trade price and the midpoint; realized spread—effective spread adjusted for subsequent price movement.
Amihud illiquidity ratio is the ratio of absolute daily return to trading volume. A high value indicates illiquidity: a small volume causes significant price movement. This metric is popular in academic research due to its simplicity of calculation from readily available data.
Price impact is the change in price caused by a trade. For large orders, price impact can be significant and represents implicit trading costs. Empirical studies show that price impact grows approximately as the square root of the trade volume.
Explicit Transaction Costs
Explicit costs are direct payments for conducting a transaction.
Brokerage commission is the fee paid to the broker for order execution. Competition and technology have significantly reduced commissions: many online brokers offer "zero" commissions for retail clients (earning from payment for order flow).
Exchange fees are payments to exchanges for order execution and access to data. Models differ: maker-taker pricing pays for consuming liquidity and rewards for providing; taker-maker pricing does the opposite; flat fee charges the same fee.
Transaction taxes exist in a number of jurisdictions (stamp duty in the United Kingdom, FTT in some European countries). Discussions about introducing a financial transaction tax in the US and EU continue, with arguments about reducing speculation versus the risk of decreasing liquidity.
Implicit Transaction Costs
Implicit costs are hidden losses arising from trading.
Bid-ask spread: by buying at ask and selling at bid, the investor loses the spread amount. For active traders, the spread is a significant drag on returns.
Market impact—the price change caused by one's own order. A large buy order raises the price, worsening execution conditions. Market impact is especially significant for institutional investors with large positions and for low-liquidity assets.
Opportunity cost arises when an order is not executed or executed partially. If the price moves away, the investor misses the opportunity.
Delay cost—losses from delay between making the investment decision and its implementation.
Implementation Shortfall
Implementation shortfall is a comprehensive metric measuring the total costs of implementing an investment decision. It compares the hypothetical result of immediate execution at the decision price with the actual result.
Components of implementation shortfall: delay cost (between the decision and order submission), market impact (influence of execution on price), timing cost (price change during execution), opportunity cost (unexecuted portion).
Analysis of implementation shortfall allows one to assess execution quality and optimize trading strategies.
Managing Transaction Costs
Algorithmic execution uses computer algorithms to optimize trading.
TWAP (Time-Weighted Average Price) evenly distributes the order over time.
VWAP (Volume-Weighted Average Price) synchronizes execution with market volume.
Implementation Shortfall minimizes total costs taking into account the risk-return tradeoff.
Choice of venue impacts costs: different exchanges and ATS offer varying spreads, depth, and fees.
Smart Order Routing automatically directs orders to optimal venues.
Trade timing: liquidity varies throughout the day. Usually, liquidity is higher at open and close (auctions), lower in the middle of the day. For large orders, it may be advantageous to use the closing auction.
Dark pools and block trading allow large orders to be executed without disclosing information, reducing market impact. However, execution is not guaranteed, and there is a risk of information leakage.
Liquidity as a Risk Factor
Illiquidity premium: academic studies show that illiquid assets offer higher expected returns as compensation for illiquidity risk. Investors should take this into account when forming a portfolio.
Liquidity as systemic risk: liquidity can suddenly disappear during periods of stress (flight to quality), intensifying market shocks. The events of 2008 showed how illiquidity spirals can turn solvent institutions into bankrupts.
§ Act · what next