Factor premia
TheoryDefinition
Risk factor premia are persistent, documented sources of excess return that show up across decades of market data and across countries. They go beyond the simple market (beta) factor from CAPM and explain return variation that the market factor alone can’t.
Academic research has identified a handful of factors that earn long-run premia. The most well-documented are:
Market (beta) — the broad stock market beats cash and bonds over long horizons. About 5–7% per year over the risk-free rate.
Value — cheap stocks (low price-to-book, low P/E) beat expensive stocks. Historical premium ~3–4% per year; has underperformed 2010–2020. ETFs: VLUE, IWD, RPV.
Size — small-cap stocks beat large-cap stocks. Premium ~2–3% per year historically; weakest of the main factors. ETFs: IJR, VB.
Momentum — stocks that went up over the past 6–12 months keep going up for another few months. Premium ~6–8% per year but with crash risk. ETFs: MTUM, PDP.
Quality — profitable, stable, low-debt companies beat junky companies. Premium ~3–4% per year; lower drawdowns. ETFs: QUAL, SPHQ.
Low volatility — less volatile stocks earn equal or higher returns than volatile stocks, with much lower risk. Violates CAPM. ETFs: USMV, SPLV.
Profitability — high gross-profits-to-assets companies outperform. The Novy-Marx/Fama-French profitability factor. ETFs: COWZ (free cash flow yield), QUAL.
Investment — companies that invest less (conservative) outperform companies that invest aggressively. Part of Fama-French 5-factor model.
Why do these premia exist? Two camps: (1) risk-based — these factors carry risks not captured by beta (distress, tail risk, illiquidity); (2) behavioral — investor biases (overreaction, overconfidence, attention) create mispricings. Both are probably partially true.
Important caveat: factor premia are long-run averages. Any single factor can underperform for 10+ years. Multi-factor portfolios smooth the ride.
Academic research has identified a handful of factors that earn long-run premia. The most well-documented are:
Market (beta) — the broad stock market beats cash and bonds over long horizons. About 5–7% per year over the risk-free rate.
Value — cheap stocks (low price-to-book, low P/E) beat expensive stocks. Historical premium ~3–4% per year; has underperformed 2010–2020. ETFs: VLUE, IWD, RPV.
Size — small-cap stocks beat large-cap stocks. Premium ~2–3% per year historically; weakest of the main factors. ETFs: IJR, VB.
Momentum — stocks that went up over the past 6–12 months keep going up for another few months. Premium ~6–8% per year but with crash risk. ETFs: MTUM, PDP.
Quality — profitable, stable, low-debt companies beat junky companies. Premium ~3–4% per year; lower drawdowns. ETFs: QUAL, SPHQ.
Low volatility — less volatile stocks earn equal or higher returns than volatile stocks, with much lower risk. Violates CAPM. ETFs: USMV, SPLV.
Profitability — high gross-profits-to-assets companies outperform. The Novy-Marx/Fama-French profitability factor. ETFs: COWZ (free cash flow yield), QUAL.
Investment — companies that invest less (conservative) outperform companies that invest aggressively. Part of Fama-French 5-factor model.
Why do these premia exist? Two camps: (1) risk-based — these factors carry risks not captured by beta (distress, tail risk, illiquidity); (2) behavioral — investor biases (overreaction, overconfidence, attention) create mispricings. Both are probably partially true.
Important caveat: factor premia are long-run averages. Any single factor can underperform for 10+ years. Multi-factor portfolios smooth the ride.
Example
A factor ETF like MTUM (momentum) has delivered ~2–3% annualized excess return versus the S&P 500 since inception, but with occasional 20%+ drawdowns during momentum crashes (e.g., 2009 rally off the bottom, 2016).
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