Factor Investing: Your Guide to Value, Momentum, Quality and Size

Factor investing is a rule-based investment strategy that deliberately invests in stocks with measurable characteristics, such as cheap valuation, high profitability or strong momentum. These characteristics are considered statistically proven drivers of returns and risk. The goal of factor investing is to achieve higher risk-adjusted returns than a broad market index. The approach is typically implemented through cost-effective ETFs that follow clear, transparent criteria rather than subjective assessments.

What Factor Investing Means at Its Core

Factor investing, also often called factor investing or smart beta investing, bridges two worlds. On one side stands passive indexing by market capitalization, on the other active stock picking.

Factor investing sits right in between: it follows fixed rules, but selects specific securities with certain characteristics. These characteristics are recurring hallmarks of stocks for which a risk premium is expected over the long term.

This premium is not a guarantee. Its success depends heavily on how cleanly the strategy is constructed.

Why Empirical Data Forms the Foundation

The approach is based on stock prices and financial information, not on forecasts from individual analysts. Statistically, the returns and risk of a stock portfolio can be explained by over 90 percent when measuring the so-called factor exposure. This is exactly where the idea comes in: measurable characteristics instead of gut feeling.

The Scientific Roots

Research on these characteristics reaches back decades. The foundation was laid in several stages.

From Single-Factor Model to Five-Factor Model

• 1960s: The Capital Asset Pricing Model recognized only one factor, market risk (beta).
• 1981: Rolf Banz discovered the size factor using 40 years of data.
• 1992/1993: Eugene Fama and Kenneth French introduced their three-factor model (market risk, size, value).
• 1993: Jegadeesh and Titman documented the momentum factor.
• 2015: Fama and French expanded their model to five factors.

What Research Recognizes Today

Over 50 years, hundreds of such characteristics have been described. Many of them are statistically questionable. Only a few remain broadly recognized: size, value, momentum and quality. Anyone who understands these criteria has grasped the essence of the topic.

What Factors Exist?

The established factors work differently depending on the market phase. They are not interchangeable, and no stock can be reduced to a single characteristic.

Value: Cheaply Valued Securities

Value stocks are low-valued according to metrics such as the price-to-earnings ratio or book value. Often, such value stocks also have above-average dividend yields, which makes them attractive for income-oriented investors.

Historically, they achieved higher returns than expensive growth stocks. The factor is considered counter-cyclical. For investors interested in value investing in 2026, one question remains open: Fama and French noted in 2020 that for the US market it was not definitively clear whether the value factor still exists. Anyone taking value investing in 2026 seriously as a strategy should factor in this uncertainty.

Momentum: The Trend as a Signal

The momentum factor bets on stocks with recent positive price performance. The assumption: a trend continues in the short term. This makes the factor pro-cyclical.

Those pursuing a momentum strategy buy strength and exit weakness according to clear rules, not by feeling. A typical momentum strategy looks at price performance over the past 6 to 12 months and rebalances regularly.

Quality: Solid Fundamentals

The quality factor favors companies with high profitability and low leverage. Such companies tend to achieve better results. The factor appeals to many investors because it focuses on substance rather than short-term price movements.

Balance sheet quality counts more than momentum of a trend. Quality & Co are often viewed as a defensive anchor during difficult market phases, and many investors appreciate this quality when seeking to avoid volatility. Quality & Co can also be combined well with other characteristics.

Size: Small and Mid-Cap Companies in Focus

Small and mid-sized companies tend to achieve higher returns over the long term than large ones. The size factor directly ties to company size and is counter-cyclical.

Small caps account for around 15 percent of total market capitalization of the global stock market, but play a minor role in the MSCI World. The small company size brings higher volatility, but historically also a noticeable premium.

Low Volatility: Steadier Price Movements

The low volatility factor focuses on stocks with lower volatility and lower market risk. The goal is a better ratio of return to fluctuation. Investors who value a quieter portfolio find a suitable alternative to traditional indices here.

Factor Premiums in the Return Check

What does factor investing concretely deliver in additional returns? The answer is more sober than some marketing texts promise.

Realistic Numbers on Factor Premium

• Historical factor premiums on the global market (1975 to 2020, long-only) typically lie at 1 to 3 percent per year excess return versus the benchmark, before costs and taxes.
• Assets invested in factor strategies rose over the last decade by around 50 percent, from about 4 to over 6 trillion US dollars.
• The global ETF industry managed around 12.5 trillion US dollars at the end of May 2024, with a growing share of factor-based products.

Such figures make clear how much this strategy has evolved from a niche to a mainstream market in recent years.

Why Patience Decides Success

A factor premium is not a regular payment. Over single years or even decades, it can turn negative.

Only over very long periods, often 15 years and more, does it statistically show itself to be reliably positive. Those who cannot endure these dry spells often give up the excess return at the most inopportune time.

Implementing Factor Investing Through ETFs

For private investors, buying corresponding ETFs is the most practical way. Such a fund tracks an index that selects and weights stocks according to fixed filter criteria. These index funds are transparent, cost-effective and traded daily on stock exchanges. Because the filter criteria are disclosed, every investor knows exactly how the index fund selects its securities.

Individual Funds or Multifactor ETFs?

Fundamentally, there are two ways. You can combine individual factor ETFs, such as a value and a momentum fund.

Or you can use multifactor ETFs that bundle multiple characteristics in one product. Well-known providers like iShares offer both single-factor and multifactor funds in their range.

The Problem of Unintended Correlations

Mixing multiple individual funds risks unintended effects. A small-cap fund often contains growth stocks, a value fund also contains large-cap stocks. This way, characteristics partially offset each other. These unintended correlations diminish the hoped-for effect of factor strategies.

Integrated Multifactor Investing as a Better Solution

Instead of mechanically combining finished funds, integrated factor investing goes one level deeper. Here, at the stock level, only those securities are selected that simultaneously meet multiple criteria, such as value, quality and momentum together. This integrated approach is precisely what makes factor investing attractive for many institutional investors.

Why Construction Matters

The advantage: unintended bets on individual countries, sectors or securities can be limited. A value portfolio can otherwise unintentionally become a regional bet.

A low-risk strategy can unintentionally build high interest rate sensitivity by overweighting utilities. Clean construction prevents such risks.

Opportunities and Risks at a Glance

Factor investing opens opportunities for systematic excess returns. At the same time, it brings its own risks that investors should be aware of.

The Main Opportunities

• Systematic, rule-based investment strategy without subjective forecasts.
• Prospect of a factor premium and thus outperformance versus the broad market.
• Wide selection of exchange-traded funds at low costs.

The Central Risks

• Long dry spells: Premiums can be absent for years.
• Implementation costs: Transaction costs, lending fees and taxes reduce returns.
• Crowding: When too many investors follow the same strategy, returns erode.
• Factor timing: Attempting to predict the next strong characteristic is as difficult as forecasting the market.

How Much Factor Belongs in Your Portfolio?

Many private investors ask themselves whether a 70/30 or 80/20 portfolio is the better basis. These allocations concern the weighting between developed and emerging markets and initially say nothing about the underlying characteristics.

Factor ETFs as a Supplement

In practice, a broad index like the MSCI World or the S&P 500 serves as the core. Factor ETFs are added as a targeted supplement. This keeps the basic structure robust while factor strategies are intended to tap additional sources of return.

Bonds and other securities also belong in the overall picture depending on your risk tolerance. Such diversification across multiple asset classes smooths overall risk.

A Possible Structure

1. Broad equity index as foundation, such as MSCI World or S&P 500.
2. One to two factor ETFs or a multifactor ETF as a supplement.
3. Bonds to manage fluctuations and overall risk.

The 5-10-40 Rule and Legal Limits

The 5-10-40 rule comes from fund law. It limits how much a fund can invest in individual issuers. A security may account for at most 5 percent of fund assets, in exceptions up to 10 percent.

Positions over 5 percent may together reach at most 40 percent. This rule ensures diversification and limits concentration risks, even in factor-based funds.

Best Practices for Implementation

From research and practice, clear guidelines can be derived. They help avoid typical investment mistakes.

Invest Disciplined and Long-Term

• Diversify: Spread across multiple characteristics rather than betting on a single one.
• Combine integrated: Prefer multifactor ETFs that select securities at the stock level.
• Choose a long horizon: Plan for at least 10 to 15 years.
• Lower costs: Use cost-effective funds and factor in all ancillary costs.
• Stay realistic: A factor premium of 1 to 3 percent per year is a plausible range.

Choose Scientifically Founded Factors

Focus on characteristics with broad consensus: size, value, momentum and quality. Exotic constructions without solid data backing often promise more than they deliver. A sober analysis of characteristics protects against inflated expectations.

Recent Developments in Factor Investing

The market remains in motion. Factor investing has evolved from an academic niche to mainstream. Institutional and private investors today use the strategy as a matter of course.

New Data Sources and ESG

Factor-based indices are becoming more numerous, and sustainability criteria are increasingly flowing into the selection. Traditional signals like the price-to-book ratio reach their limits in an economy marked by intangible assets.

New definitions of these characteristics are emerging to close this gap. Data providers are increasingly tapping alternative sources to more precisely reflect a company's valuation.

Who Factor Investing Suits

Factor investing suits investors with a long time horizon, patience and willingness to endure dry spells. Those seeking quick gains or wanting to tactically time factors will likely be disappointed. The strategy rewards discipline and a consistent buy-and-hold approach.

Clear Expectations as Foundation

A factor premium is a tendency, not a promise. It shows itself over long periods, not from quarter to quarter. Investors who internalize this perspective use such characteristics for what they are: a tool for structured, long-term investments. And long-term investments demand above all one thing: enduring weak phases.

Frequently Asked Questions About Factor Investing

Are Multifactor ETFs Worthwhile?

Yes, provided they are constructed in an integrated manner. A well-built multifactor ETF avoids unintended correlations and bundles multiple sources of return in one product. This reduces effort and makes the portfolio more manageable.

Which Factor ETF is the Best?

There is no single best factor ETF. Which characteristic is ahead at any given time is scarcely predictable. Therefore, spreading across multiple characteristics is usually smarter than searching for the one winner.

What Distinguishes Smart Beta from Active Investing?

Smart beta investing follows fixed, transparent rules and dispenses with subjective assessments. Active management, by contrast, relies on the forecasts of a fund manager.

Factor investing clearly belongs on the rule-based side. This is precisely why smart beta investing is a cost-effective alternative to traditional active funds for many private investors.

Is It Worth the Effort for Private Investors?

For investors with a long horizon, a modest allocation to factor-based funds can improve expected returns. Decisive are low costs, patience and refraining from factor timing.

Investors who meet these conditions will find in factor strategies a well-considered supplement to the broad market. Those who do not meet these conditions should stick with the simple world index as the more solid choice.