Insight Factor investing foundations: Five equity factors

This is the second of a three-part series on the foundations of factor investing. The first article explained what factors are, why factor premiums may exist and how factor investing differs from traditional active management and market-cap-weighted indexing. This second article examines five widely used equity style factors, while the final article explores single- and multi-factor portfolios and active and index-based implementation.

The first article introduced factors as measurable characteristics that may help explain differences in securities’ risk and return. This article moves from the framework to the building blocks. Five factors appear repeatedly in equity research and live strategies: value, size, momentum, volatility, and quality. 

Value: paying less for fundamentals

Value strategies favor securities priced at a discount relative to measures of fundamentals. Common metrics include earnings, book value, dividends and cash flow. The rationale is intuitive: investors may overpay for attractive growth stories or become too pessimistic about companies facing temporary difficulties. Alternatively, cheaper companies may carry greater economic or financial risk, and the prospective premium may compensate investors for bearing it.

The main challenge is distinguishing a mispriced company from one whose low valuation reflects deteriorating fundamentals. Accounting measures may also become less informative for businesses built around intangible assets. For this reason, many strategies combine several valuation measures and introduce quality or momentum checks to reduce exposure to potential “value traps”.

Size: looking beyond the largest companies

The size factor tilts toward smaller companies. Possible explanations include lower liquidity, less analyst coverage and greater sensitivity to financing conditions or the economic cycle. Smaller companies may also have more room to grow, although growth alone does not ensure attractive returns.

The academic evidence for size is less consistent than for some other factors and can depend on how micro-cap stocks, liquidity and quality are treated. Low Size strategies tend to load higher on equity market beta, which explains large parts of a potential Size premium. Furthermore, implementation at scale is limited for the factor given the comparatively low size of the stocks and thus liquidity of the strategy. Size may nevertheless influence portfolio construction by reducing the dominance of the largest companies and broadening the opportunity set. Investors should examine whether a strategy is capturing a genuine small-company effect or simply taking unintended liquidity and quality risks.

Volatility: challenging a simple risk-return assumption

Volatility strategies favor securities whose prices have fluctuated less than those of their peers. Historically, low volatility equities have often delivered stronger risk-adjusted returns than a simple model would suggest. One explanation is that leverage constraints encourage investors seeking higher returns to buy high-beta securities, making them relatively expensive. Benchmark pressure and a preference for exciting stocks may reinforce the effect.

Low volatility portfolios could develop sector or interest rate sensitivities because defensive industries often dominate the eligible set. They may also lag sharply in fast, speculative rallies. The objective is not to eliminate loss, but to reshape the pattern of equity risk. Construction constraints are important if investors want lower volatility without excessive concentration.

Momentum: following persistent trends

Momentum favors recent winners and reduces exposure to recent losers. It is commonly linked to behavioral biases: investors may absorb new information gradually, anchor to old expectations or follow existing trends. Earnings revisions may provide a related signal because changing analyst expectations may precede full adjustment in market prices.

Momentum may diversify value because the two often favor different securities. However, it could involve high turnover and may suffer abrupt reversals when market leadership changes. Signal diversification, trading discipline and controls around crowded positions are therefore particularly important.

Quality: focusing on resilient businesses

Quality strategies seek companies with characteristics such as strong profitability, stable earnings, healthy cash generation and conservative balance sheets. The rationale is that markets may underappreciate the persistence of good businesses or overpay for more speculative opportunities. Quality may also provide resilience when economic conditions weaken.

Quality is harder to define than its label implies. Brand strength, management capability and competitive advantage may be economically important but difficult to quantify. A narrow screen can also exclude young companies that are reinvesting heavily. Robust strategies therefore tend to use multiple observable measures while recognizing what the data cannot capture.

Why definitions matter

Two strategies carrying the same factor label may have materially different portfolios. A value strategy based on book value may differ from one based on cash-flow yield. A quality portfolio focused on profitability may not resemble one built around low leverage. Rebalancing schedules, sector limits, security weighting and transaction-cost controls create further differences.

Investors can therefore look beyond labels and ask three questions: What is the signal? How is it translated into holdings? What risks emerge from that process? This due diligence helps separate intended factor exposure from unintended bets.

No factor leads in every environment

Factors may experience long periods of relative weakness. Value may struggle when investors favor rapidly growing companies. Momentum may reverse when market leadership turns abruptly. Smaller companies may be vulnerable when liquidity tightens. Low volatility and quality may lag in strong risk-on rallies. These patterns are observations, not reliable timing rules. Economic turning points are difficult to identify consistently in advance.

This uneven behavior creates the bridge to Article 3. If factors are distinct and leadership rotates unpredictably, investors need to decide whether to hold a single factor, combine several, or use factors to complement existing managers. The final article addresses those choices and focuses on implementation rather than labels.

Investment Risks

The value of investments and any income will fluctuate (this may partly be the result of exchange-rate fluctuations), and investors may not get back the full amount invested. The information is provided for illustrative purposes only and does not represent investment advice or an offer to buy or sell any investment strategy.