For years, investors have debated one of the biggest questions in portfolio management: should you choose active investing or passive investing?

Passive investing, usually through index funds or ETFs, has become incredibly popular over the past two decades. Legendary investor Warren Buffett has even recommended that most investors buy a low-cost S&P 500 index fund rather than try to beat the market. His reasoning is straightforward: most professional money managers fail to consistently outperform the market after accounting for fees.

On the surface, the evidence appears overwhelming. Numerous academic studies have found that the majority of actively managed mutual funds underperform their benchmarks over long periods when fees and trading costs are accounted for. This has led many investors to conclude that passive investing is always the superior choice.

But the reality is more nuanced.

Why most active managers struggle

To understand the debate, it helps first to define active investing.

Traditional active managers attempt to outperform the market by selecting individual stocks they believe will outperform or by trying to time market movements. This requires identifying securities that are mispriced relative to their true value.

The challenge is that financial markets are highly competitive. Every day, millions of investors, including institutional investors, hedge funds, pension funds, and sophisticated trading firms, analyze the same information. When new information becomes available, stock prices adjust remarkably quickly.

As researchers at the University of Chicago Booth School of Business explain, active management is extremely difficult because markets are efficient enough that consistently finding mispriced securities is rare. Even when skilled managers do identify opportunities, higher trading costs, management fees, and taxes often eliminate much of the advantage.

This explains why so few traditional active funds consistently outperform broad market indexes over long periods.

Active investing is a negative-sum game

One of the most powerful concepts in investing comes from Nobel Prize-winning economist William F. Sharpe.

His research demonstrated that, before costs, the average active investor must earn the same return as the market because active investors collectively own the market. After subtracting management fees, trading costs, commissions, and taxes, the average active investor must underperform.

In other words, active investing is a negative-sum game.

Someone will always outperform. Someone else will underperform. But once costs are factored in, the average actively managed dollar must earn less than the market itself.

This arithmetic helps explain why Buffett continues to advocate for low-cost index investing for the average investor.

So, is passive investing always best?

Not necessarily.

One misconception is that passive investing means “doing nothing.”

In reality, every index is built using a set of rules. Someone decides which companies qualify for inclusion, how they are weighted, when securities are added or removed, and how corporate actions are handled. Those are all active decisions.

For example, the S&P 500 only includes approximately 500 large U.S. companies. It excludes thousands of smaller businesses, international companies, and many publicly traded firms simply because they don’t meet the index’s criteria.

Likewise, indexes periodically rebalance their holdings, forcing them to buy stocks after they have qualified for inclusion and sell stocks after they have fallen out of the index. This process can create hidden trading costs that aren’t reflected in a fund’s management expense ratio.

Passive investing is therefore not completely passive; it simply follows predetermined rules.

A different kind of active investing

This is where the discussion becomes more interesting.

Many people think investing only offers two choices:

  • Pick stocks and try to beat the market.
  • Buy an index fund.

But there is actually a third approach.

Rather than attempting to identify mispriced stocks, some investment strategies seek to systematically capture sources of expected returns that decades of academic research have identified.

These strategies do not rely on forecasting earnings, predicting recessions, or guessing which stock will outperform next year.

Instead, they build diversified portfolios that emphasize characteristics associated with higher expected long-term returns, such as smaller companies, value stocks, and companies with higher profitability, while maintaining broad diversification and disciplined implementation.

This approach accepts that markets do an excellent job of incorporating information into prices while recognizing that not all stocks have identical expected returns.

Discipline matters more than prediction

The greatest advantage any investor can have isn’t finding the next winning stock. It’s maintaining discipline.

History shows that investors often struggle more with their own behaviour than with investment selection. Market downturns can tempt people to sell after prices have already fallen. At the same time, periods of strong performance often encourage investors to chase recent winners.

Whether an investor owns actively managed funds or passive index funds, emotional decision-making can significantly reduce long-term returns.

A disciplined investment process, consistent rebalancing, broad diversification, and staying invested during periods of volatility often have a much greater impact on long-term success than attempting to predict short-term market movements.

The bottom line

The active-versus-passive debate often oversimplifies investing.

Traditional active stock picking has historically struggled to outperform after fees and costs, which is why low-cost index funds have become such a popular solution. For many investors, they remain an excellent choice.

However, passive investing is not entirely passive, and indexing itself involves numerous active decisions.

Rather than asking whether active or passive investing is “better,” investors may be better served by asking different questions:

  • Is my portfolio globally diversified?
  • Are investment costs reasonable?
  • Am I investing based on evidence rather than predictions?
  • Do I have a disciplined process that I can stick with during market volatility?

Ultimately, successful investing isn’t about finding a perfect strategy. It’s about choosing an approach grounded in sound research, keeping costs under control, remaining diversified, and maintaining the discipline to stay invested over the long term.

Those principles have consistently proven to matter far more than predicting which stock or which fund manager will be the next big winner.