How do I quantify the opportunity cost of unexecuted trades?

Question

AcadiFi · Accepted Answer

Opportunity cost is the missed return on the portion of an order that was not executed (or was executed too late). In Perold's implementation shortfall it's a distinct component. Standard formula: Opportunity Cost = (End-of-horizon Price − Decision Price) × Shares Unfilled. For a buy order, if the price rose after decision and you didn't fill all shares, you missed that appreciation. For a sell order, if the price fell after decision and you didn't fill, you missed that savings. Example: Portfolio manager Anneliese Groot decides to buy 200,000 shares of a biotech at $34.50 (decision price). Her algo fills only 120,000 over the day at avg $34.72. The stock closes at $36.10 (news broke mid-day). Unfilled = 80,000. Opportunity cost = (36.10 − 34.50) × 80,000 = $128,000. ```mermaid flowchart TB A[Order 200k
@ $34.50] --> B[Fill 120k
@ $34.72] A --> C[Miss 80k] C --> D[Close $36.10] D --> E[Opp Cost
$128k] ``` Key nuances: 1. **Choice of horizon**: standard is end-of-day or cancellation time. Longer horizons make opportunity cost more volatile and potentially misleading. 2. **Passive limit orders** have high opportunity cost because they often don't fill; aggressive orders cut opportunity but raise impact. 3. **Risk aversion trade-off**: a trader afraid of impact might under-fill and pay opportunity cost instead — rational if impact estimates are conservative, costly if not. For risk management, opportunity cost is the reason liquidation-horizon VaR matters: if forced selling can't complete in one day, residual-position moves hit the book as opportunity loss. Modeling it alongside impact gives a fuller liquidity-adjusted risk picture.

How do I quantify the opportunity cost of unexecuted trades?

Master Part II with our FRM Course

Related Questions

Practice Questions