What Is Market Impact?
Market impact is the price movement caused by executing a trade. A market buy order consumes available sell orders (asks) from lowest to highest price, moving the price upward. The larger the order relative to available liquidity, the greater the market impact. For small retail orders, impact is negligible. For institutional-size orders, impact can be substantial and must be carefully managed.
How Market Impact Works
Market impact has two components: temporary impact (the price displacement during execution that partially reverses after) and permanent impact (the lasting price change reflecting new information conveyed by the trade). Total execution cost includes the spread, market impact, and any exchange fees. Impact models estimate the cost as a function of order size, volatility, average volume, and execution speed.
Why It Matters for Traders
Managing market impact is critical for any trader moving significant size. Strategies to reduce impact: use limit orders instead of market orders, split large orders across time using TWAP or VWAP algorithms, trade during high-volume periods when liquidity is deepest, and consider using dark pools or OTC desks for very large trades. Even for smaller traders, understanding market impact explains why large-cap liquid assets are easier to trade profitably than illiquid small-caps.
