Your fund rose 60% over two years. Your account holds less than you put in.
Say you invest $200 when a fund unit costs $10. A year later, you add $1,800 at $20. At the end of the second year, the price is $16 and your account is worth $1,760. You contributed $2,000.
Both numbers can be right. One tracks the fund's price; the other tracks money invested at different times. Before blaming the investor, notice what the statement leaves out: when that extra $1,800 became available.
The fund rose, but your dollars did not
Your first $200 buys 20 units at $10 each. The later $1,800 buys 90 more at $20. That gives you 110 units, most bought after the price doubled.
Ending account value = (20 + 90) × $16 = $1,760.
Your first deposit grows from $200 to $320. The second shrinks from $1,800 to $1,440. A $120 gain and a $360 loss leave you $240 short. Most of your money missed the rise and caught the fall.
That $240 is a dollar loss. The fund's 60% is its cumulative return over two years: a $6 gain on a $10 starting price. Neither is an annualized investor return.
Time-weighted and money-weighted returns separate these questions. The first tracks the investment's performance; the second also reflects the timing and size of your deposits and withdrawals.
What a return gap tells you
An investor return gap is investor return minus fund return. Compare the same dates, with both returns annualized or both cumulative.
A negative gap means investor dollars lagged the fund. Positive means they did better; zero means they matched.
Behavior gap is a familiar name for this difference. A gap is a measurement, not a diagnosis.
In Mind the Gap 2024, Morningstar estimated that the average dollar invested in US mutual funds and ETFs earned 1.1 percentage points less per year than the funds over the decade ended December 31, 2023.
The report warns that payroll saving and rebalancing can create a gap while serving a sensible plan. Fund flows show money moving; they don't show why.
The estimate describes the average dollar, not the average person. It is a historical shortfall, not a yearly fee or extra return everyone could have earned.
One deposit, two different stories
That $1,800 deposit could have either of these explanations:
- A bonus just arrived. You invest it as planned. It was never available at the start.
- A rally made you comfortable. The cash was ready to invest all along. You waited until the fund's rise made buying feel safe.
The account statement is identical. The reason for the deposit is not.
Performance chasing means choosing or adding to an investment mainly because it recently did well. In the second story, the rally supplies reassurance. A changed goal or new evidence about the investment could give you a separate reason to buy after a rise.
A good run can start to feel like evidence of another one, a temptation explored in recency bias and market timing.
A $200 monthly contribution can simply follow payday. You might withdraw money for a bill or rebalance to restore your chosen investment mix.
A necessary withdrawal before a rally can lower your measured return. Missing that rally does not make the bill optional.
| Cash movement | Evidence still needed |
|---|---|
| $1,800 deposit | When cash arrived; why you bought |
| Bill withdrawal | Amount needed and due date |
| Rebalance | Rule that triggered it |
A statement has the transaction dates and amounts. The missing pieces are the original plan, when money was available or needed, and the reason given at the time.
Review one transaction
The cash flows explain your $1,760 balance. Why you made the second deposit is still unknown. Investing the full $2,000 at the start was only an option if you had it then.
A brief explanation saved when you trade helps separate the two stories later: "Bonus received today; invested for retirement under my existing plan." That is the start of an investing journal, which we will build near the end of this track. Your investment policy, the rules you set for your goals and portfolio, supplies the plan to check it against.
A higher ending price would not make a performance-chasing decision more carefully reasoned. A lower one would not make a newly received bonus available a year earlier. Judge the decision with the information you had when you made it.
Try that distinction on PDF page 3 of the Morningstar report linked above. In the Introduction, find the two routine investing habits that can create a gap. Why does that caveat rule out diagnosing panic selling from a negative gap alone?
For the opening statement, "reason unknown" is a complete answer. The next lesson, loss aversion, examines why a loss can carry more weight than an equal gain.
In short
- A fund can rise while your invested dollars lose money.
- Deposits, withdrawals and rebalancing can create a return gap while serving a sound plan.
- A return gap reveals a difference in results; it cannot reveal an investor's motive.
- Judge the decision using the money and information available at the time.