Benchmarking

Why most private investors underperform the market

The market returns a certain percentage. The funds that track it return slightly less. The people in those funds earn less again than the funds themselves. That last gap, the behavior gap, is measured every year in Morningstar's Mind the Gap studies. It lands between 1 and 1.5% per year and comes from timing rather than from the funds.

These investors are not picking bad funds. They earn less than the funds they hold, which means the shortfall comes from the timing of their own deposits and withdrawals.

This article explains what the gap measures, where the money goes, why the pattern persists among intelligent people, and how to find out whether your own portfolio has a gap.

What the behavior gap measures

The behavior gap is the distance between two return numbers calculated from the same account. A fund's published return is time-weighted. It measures what the fund did, regardless of when anyone's money arrived.

An investor's personal return is money-weighted. Every euro counts for as long as it was invested, so late deposits and early withdrawals change the number. When money arrives after the good returns and leaves before the recovery, the money-weighted number falls below the time-weighted one, and the difference is the gap.

The full mechanics of the two measures are in time-weighted vs money-weighted return. The short version is that the gap is your timing, isolated from your picks, expressed as a percentage per year.

Research on investor behavior finds the same pattern across countries, decades and fund types, in index funds and in sector funds alike. The gap is generally widest in the most volatile funds, because volatility creates the most occasions to buy or sell at the wrong moment.

Where the money goes

Buying after a rise. Money flows in after rallies, at the prices that make future returns smaller. Deposits after a fall are rarer. The studies find deposits concentrated in the months after a rise.

Selling winners and keeping losers. Taking a profit feels responsible, and realizing a loss feels like admitting a mistake. The result is a portfolio that sheds what works and keeps what does not. The accounting habit behind this, treating a loss as not yet counted until you sell, is explained in realized vs unrealized gains.

Trading itself. Barber & Odean found that the more retail investors trade, the worse they do. Every trade is a fee, a spread and a new chance to be wrong.

Untracked experiments. The crypto phase, the leveraged ETF week and the options month add up to about a percent a year that nobody counts. They often sit at a second or third broker so that they stay out of the main portfolio's statistics, which is why pulling every account into one dashboard is about completeness rather than convenience.

Why the pattern persists

None of these leaks come from a lack of intelligence. They come from normal human reactions in a domain that punishes them. Losses hurt roughly twice as much as gains of the same size feel good, so realizing a loss gets postponed while gains get taken early.

Recent events dominate the sense of what comes next, so a market that has risen recently feels safer, even though the prices are higher. Nearly everyone rates their own judgment above average, so each trade feels like the exception to statistics compiled from other people's trades.

Markets are one of the few environments where the intuitive move is reliably the expensive one. Confidence arrives after prices rise, and fear arrives after they fall. An investor who follows those feelings ends up buying high and selling low. The behavior gap is what that costs, measured across many investors.

A worked example of a fixed schedule

Dollar-cost averaging, buying a fixed amount on a fixed schedule, is usually presented as a way to feel calmer. It is also a piece of arithmetic. Suppose you invest €300 a month in a fund whose price goes €10, €12 and €8 over three months. You buy 30 shares, then 25, then 37.5.

That is 92.5 shares for €900, an average cost of about €9.73 per share, below the €10 average of the three prices. A fixed euro amount buys fewer shares when they are expensive and more when they are cheap, which is the opposite of what the feelings described above lead to.

This does not mean that averaging in beats a lump sum. Over long periods markets rise, so earlier money tends to do better. What a standing order does is execute on schedule whether the month felt good or bad, and the behavior gap lives in the difference between those two states.

What steady contributions add up to over decades is worked out in the compound math of monthly investing.

What the measurements point at

The studies that measure the gap keep pointing at the same three things, and none of them is trading better. The first is a deposit schedule that does not depend on how the month felt. The second is a record that still contains the closed positions and the fees. The third is a benchmark built from your own cash flows.

The third one changes behavior more than any market opinion. When a simulated index portfolio that received your deposits on the same dates is always on screen, every impulse trade is visible against the result of doing nothing.

What the three have in common is that they remove decisions rather than improve them. That is the opposite of the usual reaction after discovering a gap, which is to research harder. Whether any of that belongs in your own setup is your decision.

Finding your own number

Averages say nothing about one portfolio. The question that matters is whether you have a gap, and how large it is. The check takes two comparisons.

The first is your money-weighted return against your time-weighted return. If the money-weighted number is persistently lower, your timing has cost you, and the size of the difference is roughly the annual rate of that cost. The second is your time-weighted return against an index you would buy instead. That one grades the picks themselves.

Both comparisons need your complete history, meaning deposits, withdrawals, every closed position, the fees and the experiments, because the leaks sit mostly in the parts memory has already discarded. A review that only covers the positions still open misses most of them. The complete history already exists, with dates, in the transaction export from your broker.

Why measuring changes the result

A fund manager's behavior gap is smaller than a private investor's, and the reason is that someone is watching. Numbers that are reported, compared with a benchmark and reviewed on a schedule discipline behavior by themselves.

A private investor gets the same effect from a dashboard that includes the sold positions, the fees, the experiments at the second broker and the simulated portfolio that made no decisions at all. The method is described in how to check whether you are beating the S&P 500.

BullBenchmark is built for that. It reads your full history from every broker and compares it with the index every day. It does not improve your picks. It makes the gap visible, which is the one thing a private investor can do without an opinion about the market.

BullBenchmark reads the transaction export from your broker and shows your return next to the S&P 500 and the Nasdaq 100, fed with the same deposits on the same dates, in your own currency. The first two weeks are free and no card is needed.