Quick definition An execution algorithm breaks a large order into smaller pieces and executes them over time according to a predetermined or adaptive strategy. The goal is to minimise total execution cost. What it is Institutional traders cannot execute large orders all at once without moving the market significantly. An execution algorithm automatically submits small orders throughout the trading day. VWAP algorithms follow market volume. Adaptive algorithms respond to price and volume in real time. The algorithm manages the trade-off between two costs: market impact (the cost of trading too fast) and timing risk (the cost of trading too slowly and prices moving against you). Why it matters Execution algorithms save institutional traders money. A pension fund managing 100 million dollars can execute better with a VWAP algorithm than with a single market order. The algorithm earns its fee through better execution. Execution algorithms are also a major business for brokers, who develop proprietary algorithms to attract institutional client orders. Execution Algorithm versus Manual Execution Manual execution gives the trader full control but requires constant attention. Execution algorithms are mechanical and run without intervention. Most institutional traders use execution algorithms for large orders and save manual execution for small, urgent orders. Practical example You have 5 million shares to buy. A naive approach is to buy all 5 million at market, incurring massive impact. Instead, you use a VWAP algorithm that estimates daily volume and buys roughly proportional to volume throughout the day. The algorithm automatically places orders of 100,000 to 500,000 shares at various times. By day end, you have bought all 5 million shares at an average price close to VWAP, paying only a few basis points of slippage instead of hundreds. Adaptive algorithms Simple algorithms like VWAP and TWAP follow fixed patterns. Adaptive algorithms use real-time market data to adjust trading speed. If the market is moving in your favour, you trade faster. If against you, you trade slower. See also - VWAP (Volume-Weighted Average Price) - TWAP (Time-Weighted Average Price) - Market Impact - Algorithmic Trading
