Factor Investing: Size, Value, Momentum, and Quality Explained

July 13, 2026 3 min read

Factor investing targets specific characteristics that academic research has shown to drive excess returns over the long term.

The Main Factors

FactorDescriptionHow It Works
SizeSmall-cap stocks outperform large-capSmall companies have higher growth potential
ValueCheap stocks outperform expensive onesLow price-to-book stocks have higher returns
MomentumRecent winners continue to winStocks that went up keep going up
QualityHigh-quality companies outperformProfitable, stable, well-managed companies
Low volatilityLow-risk stocks outperform high-riskDefensive stocks have higher risk-adjusted returns

Factor Performance History

FactorAnnual Excess Return (US, 1927-2023)
Size (small caps)~2-3%
Value~3-5%
Momentum~8-10% (but high turnover)
Quality~2-4%
Low volatility~1-2%

Size Factor

AspectDetails
DefinitionSmall market capitalisation companies
RationaleHigher risk, less analyst coverage, higher growth
ETF examplesIUSN (iShares World Small Cap), AVUS
RisksHigher volatility, less liquidity

Value Factor

AspectDetails
DefinitionLow price relative to fundamentals (P/B, P/E, P/S)
RationaleMarket overreacts to bad news
ETF examplesVVAL (Vanguard Global Value Factor)
RisksValue traps (cheap for a reason)

Momentum Factor

AspectDetails
DefinitionStocks with strong recent returns
RationaleInvestors underreact to new information
ETF examplesMTUM (iShares MSCI USA Momentum Factor)
RisksHigh turnover, crash risk, tax inefficient

Quality Factor

AspectDetails
DefinitionHigh profitability, stable earnings, low debt
RationaleQuality companies compound better
ETF examplesQUAL (iShares MSCI USA Quality Factor)
RisksCan be expensive (high P/E)

How to Implement

MethodHow
Factor ETFsSingle ETF targeting one factor
Multi-factor ETFsOne ETF targeting several factors
Smart beta fundsRule-based index with factor tilts
Direct stock selectionBuild your own factor portfolio

Multi-Factor Approach

CombinationWhy
Value + MomentumValue captures long-term, momentum captures short-term
Quality + Low VolatilityDefensive combination
Size + ValueSmall-cap value has strongest historical returns

Bottom Line

Factor investing targets specific return drivers: size, value, momentum, quality, and low volatility. Each factor has strong academic backing and historical evidence. Multi-factor approaches reduce reliance on any single factor. Factor ETFs make implementation simple for individual investors. Factor premiums can underperform for extended periods (value underperformed for a decade after 2007). Patience is essential.

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This content is for educational purposes only. Not financial advice. Do your own research before investing.