Risk Premium vs Behavioral Anomaly: Why Factor Returns Persist Across Regimes

The Persistence Paradox in Factor Investing

When academic literature documents an empirical anomaly, classic market efficiency suggests it should rapidly disappear. As arbitrageurs allocate capital to exploit the inefficiency, prices should adjust, eliminating future excess returns.

Yet core equity factor premiums—including Value, Momentum, Quality, and Defensive—have persisted across decades, international markets, and changing economic regimes. Why do these premia survive widespread publication?

Financial economists explain this persistence through two competing yet complementary paradigms: rational risk compensation and behavioral systematic mispricing.

The Rational Risk Paradigm: Compensation for Pain

Championed by Eugene Fama and Kenneth French (1993), the risk-based view posits that factor premiums represent fair compensation for bearing non-diversifiable, bad-times economic risk. Investors in high-loading factor portfolios suffer during specific macroeconomic downturns:

• Value Premium as Financial Distress Risk: Value companies trade at low valuation multiples because they often possess high operating leverage, elevated debt burdens, or cyclical vulnerabilities. In credit crunches or recessions, value stocks suffer severe fundamental contractions.
• Size Premium as Illiquidity Risk: Smaller capitalization firms face higher borrowing costs, lower capital market access, and greater bankruptcy sensitivity during credit contractions.
• Cyclical Factor Drawdowns: Factor strategies undergo multi-year underperformance cycles. Because human allocators have finite investment horizons, enduring extended factor drawdowns is a real economic risk that demands an equity premium.

In the rational framework, factor returns persist precisely because they are fundamentally uncomfortable to harvest.

The Behavioral Paradigm: Systematic Cognitive Biases

Conversely, behavioral theorists like Lakonishok, Shleifer, and Vishny (1994) argue that factor premiums stem from persistent cognitive errors and institutional agency frictions:

• Extrapolation Bias: Investors systematically overextrapolate recent earnings trends. They bid growth stocks to unjustified valuation premiums while excessively punishing beaten-down value companies.
• Attention and Saliency: High-beta, speculative growth companies offer lottery-like payoffs that retail and institutional investors consistently overpay to hold.
• Career Risk and Agency Constraints: Portfolio managers fear benchmark-relative underperformance. Holding consensus, highly visible growth stocks presents less reputational risk than allocating to unglamorous, depressed value or defensive companies.

Limits to Arbitrage Ensure Factor Durability

Why don't quantitative hedge funds eliminate these behavioral mispricings? The answer lies in limits to arbitrage (Shleifer and Vishny, 1997):

1. Holding Costs & Volatility: Factor anomalies carry substantial tracking error and idiosyncratic volatility.
2. Short-Selling Constraints: Borrow costs, recall risk, and liquidity constraints prevent efficient shorting of overpriced securities.
3. Capital Flight: Investors withdraw capital from active managers during cyclical factor drawdowns, cutting short arbitrage positions before convergence occurs.

Because human psychology and structural constraints remain invariant, behavioral anomalies endure alongside rational risk compensation.

Portfolio Implications

Allocators need not choose between paradigms. Both rational risk compensation and behavioral persistence reinforce the durability of multi-factor investing.

Learn how the Parallax Factor Methodology isolates durable factor exposures, and explore multi-factor screening workflows via Parallax Features.