Unit
- Factor definition: A factor is a systematic characteristic or risk that explains differences in asset returns across a broad cross-section of securities. Factors are identified through empirical research and economic theory, capturing exposures such as value, size, momentum, quality, and low volatility.
- Economic rationale: Factors earn premiums either as compensation for bearing systematic risk (risk-based explanation) or due to persistent behavioral biases that lead to mispricing (behavioral explanation). Both justifications contribute to factor premia persisting over time.
- Risk-based factors: Investors require a higher expected return for exposure to risks such as financial distress (value), illiquidity (size), or uncertainty (low volatility). These factors have high Sharpe ratios but can experience severe drawdowns during economic stress.
- Behavioral factors: Momentum arises from investor underreaction and overreaction; quality factors reflect investor preference for stable earnings. These factors exploit systematic cognitive errors that are slow to arbitrage away.
- Factor returns vs. alpha: Factor returns are common across many assets, whereas alpha is asset-specific. Distinguishing between the two is critical for performance attribution and risk budgeting.
- Factor investing history: Early work by Markowitz (1952) on diversification, Sharpe (1964) on CAPM, and Fama-French (1992) on three-factor model laid the groundwork. More than 300 factors have been documented, but only a handful are robust and economically meaningful.
- Factor investability: A factor must be implementable through liquid, low-cost portfolios. Theoretical factors that cannot be traded are of limited practical use. Common investable factors include value, size, momentum, quality, low volatility, and yield.
- Factor zoo problem: The proliferation of factors creates challenges in distinguishing true signals from data mining. Researchers use multiple testing corrections, out-of-sample tests, and economic rationale to select factors.
- Factor construction methodology: Factors are typically constructed using long short portfolios sorted on a specific characteristic, such as book to market ratio for value. Portfolio weights are often market cap weighted or equal weighted, and rebalanced periodically. Careful handling of outliers, transaction costs, and turnover is essential to ensure realistic factor returns.
- Factor timing and cyclicality: Factor performance varies across economic regimes. For example, value outperforms during economic recoveries, while low volatility tends to outperform during downturns. Understanding these cycles helps investors adjust factor exposures dynamically or maintain a diversified multi factor approach to reduce drawdowns.
- Factor correlation and diversification: Factors exhibit time varying correlations. Value and momentum are often negatively correlated, providing diversification benefits. However, correlations can become positive during crises, reducing the benefits. Monitoring realized correlations and using risk parity weighting can improve portfolio stability.
- Factor implementation costs: Real world factor portfolios incur trading costs, bid ask spreads, and market impact. Factors with high turnover, like momentum, have higher implementation costs. Investors must estimate net returns after costs and consider capacity constraints to avoid eroding factor premiums.
Risk Assessment
MEDIUM RISK
Factor investing introduces model risk: factors may stop working due to crowding, regime shifts, or data mining. Investors must regularly validate factor integrity and monitor for structural breaks. Medium risk applies to diversified factor portfolios; concentrated single-factor bets carry high risk.
Quick Revision
- Factors are systematic return drivers that explain cross-sectional differences in asset returns.
- Factor premiums arise from risk compensation and behavioral biases.
- Key factors include value, size, momentum, quality, low volatility, and yield.
- Investable factors must be implementable with low cost and adequate liquidity.
- The factor zoo highlights the need for rigorous factor selection.