Trustner AcademyTrustner AcademyCourses
Reading 1CFA L3 TradeFull chapter

Trade cost analysis and execution

In this chapter: Implementation shortfall · VWAP/TWAP and arrival-price algorithms · Market impact estimation · Manager evaluation

~3 min readLayer 4 · Professional CertificationsFree

Execution costs erode alpha. CFA L3 tests measuring trade costs and selecting algorithms.

Foundation

**Implementation shortfall (IS)**: IS = (Decision price – Execution price) × Shares + opportunity cost (unfilled orders). Measures full cost: explicit (commissions) + implicit (market impact + delay + missed opportunity). Decomposition: - Delay cost: market moved between decision and order. - Trading cost: spread + market impact. - Opportunity cost: portion not filled. **Algorithmic trading**: - **VWAP** (volume-weighted average price): trade in proportion to expected daily volume profile. Minimises tracking error vs VWAP benchmark. - **TWAP** (time-weighted): equal-sized slices over time. Simpler than VWAP. - **Arrival-price algos** (e.g., IS-aware): minimise IS by trading aggressively early when alpha decay risk high. - **Liquidity-seeking**: hunts dark pools and lit venues for blocks. - **Implementation shortfall algo**: adapts to market conditions. **Market impact**: - Temporary: pushes price during execution, recovers. - Permanent: signals information, doesn't recover. - Square-root law: impact ∝ √(order size / daily volume).

Deep Dive

**Manager evaluation framework**: - Performance: TWR, Sharpe, IR over multiple cycles. - Risk: ex-ante factor exposures, ex-post drawdowns. - Process: discipline, repeatability, edge. - People: pedigree, retention, succession. - Operations: trade execution, compliance, systems. - Fees: gross-net, hurdles, transparency. Common manager-selection mistakes: - Recency bias: chasing recent winners. - Style drift undetected. - Overweighting performance vs other factors. - Inadequate ODD. **Operational due diligence**: - Trade execution review: CTAs, broker selection. - Counterparty exposure. - Custody verification (independent custodian, not GP). - Valuation (especially for illiquid). - Compliance + audit. - Cyber.

Advanced

CFA L3 essay: "Manager X has IR of 0.8 over 5 years. Recommend whether to retain." Framework: 1. Decompose IR: factor exposure vs alpha. 2. Compare to peer median. 3. Style consistency. 4. People: any departures? 5. Process changes? 6. Fee competitiveness. 7. Cumulative due diligence. Decision: retain only if alpha is genuine, process intact, people stable, fees fair. IR alone insufficient.

Regulatory references
  • SEBI Stock Broker Regulations
  • NSE Trading Rules
  • CFA Institute Trading curriculum
Common mistakes & pitfalls
  • Comparing execution price to closing — no opportunity-cost component.
  • Not adjusting for market move during execution period.
  • Selecting manager on recent IR alone.

Frequently asked

Best algo for large orders?
Depends. VWAP minimises tracking error to VWAP. IS algo minimises arrival-price shortfall. Liquidity-seeking for blocks.
Why does manager selection require multi-cycle data?
Single cycle could be luck. Need 3+ cycles to assess skill vs random. Even then survivorship and recency bias.

Practice questions

Click each question to reveal the answer and explanation.

Q 1
IS is:
  1. (a)Decision price - close
  2. (b)Decision price - execution price + opportunity cost
  3. (c)Volume-weighted
  4. (d)Spread only
Correct: (b) Decision price - execution price + opportunity cost
IS = full cost: delay + execution + missed-opportunity vs decision price.
Q 2
VWAP algorithm trades:
  1. (a)Linearly over time
  2. (b)Proportional to expected volume profile
  3. (c)All at open
  4. (d)Block at close
Correct: (b) Proportional to expected volume profile
VWAP follows expected intraday volume curve.
Q 3
Permanent market impact:
  1. (a)Reverses
  2. (b)Reflects information signal — doesn't recover
  3. (c)Equal to spread
  4. (d)Zero
Correct: (b) Reflects information signal — doesn't recover
Permanent impact = price move that persists post-trade. Signals informed trading.
Q 4
Manager IR of 0.8 over 3 years:
  1. (a)Definitely skill
  2. (b)Could be skill or luck — need more data + qualitative
  3. (c)No information
  4. (d)Buy more
Correct: (b) Could be skill or luck — need more data + qualitative
Single 3-yr IR insufficient. Need multi-cycle, process review, attribution.
Q 5
Square-root law of market impact:
  1. (a)Impact = volume × spread
  2. (b)Impact ∝ √(order/daily volume)
  3. (c)Linear
  4. (d)Constant
Correct: (b) Impact ∝ √(order/daily volume)
Empirical regularity: impact scales with square root of order size relative to daily volume.
Educational purposes only. The numbers, returns, and examples used in this lesson are illustrative. Past performance does not guarantee future results. Mutual fund and securities investments are subject to market risks. This lesson is not investment advice; for advice tailored to your circumstances, consult a SEBI-registered Investment Adviser. Read our full disclaimer.