Time-Weighted Returns
Learn how time-weighted return links sub-period performance around deposits and withdrawals to measure investment-process performance.
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Time-weighted return measures the compound performance of the investment process while neutralising the effect of external deposits and withdrawals that the manager does not control.
Learning objectives
- Calculate linked sub-period returns around external cash flows.
- Explain why TWR is useful for comparing investment-manager performance.
- Distinguish TWR from money-weighted return and simple account-value change.
What it is
Time-weighted return splits the measurement period at external cash flows, calculates the investment return for each sub-period, and then geometrically links those returns.
This prevents a large deposit just before a rally from making the portfolio process appear more skilful simply because more money happened to be present. It also prevents a withdrawal from being mistaken for an investment loss.
Internal portfolio trades—selling BTC to buy ETH, for example—are not external cash flows. They change the portfolio holdings but not the amount of outside capital entrusted to the strategy.
How it works
Accurate valuations are required immediately before or around material cash flows. Illiquid tokens can make TWR less reliable if marks are stale or difficult to obtain.
TWR is especially useful for comparing managers or strategies where clients control deposits and withdrawals. Money-weighted return, often calculated using IRR/XIRR methods, answers a different question: what return did the actual cash invested experience given its timing?
An investor can therefore have a positive TWR strategy but a negative personal money-weighted return if most capital was added shortly before a large drawdown.
Sub-period returns must be linked geometrically, not averaged arithmetically, because investment returns compound.
Measurement methodology
| Check | Purpose | What to verify |
|---|---|---|
| Cash-flow identification | Defines sub-periods | Separate deposits/withdrawals from internal trades. |
| Valuation | Ensures accurate returns | Mark the portfolio around each external flow. |
| Geometric linking | Preserves compounding | Multiply 1 + each sub-period return. |
| Interpretation | Prevents misuse | Use TWR for process performance and MWR for investor experience. |
Worked example and thought exercise
A portfolio starts at £100,000 and grows to £110,000, a +10% sub-period return. The investor then deposits £90,000, bringing the account to £200,000. The portfolio later falls to £180,000, a −10% return for the second sub-period.
TWR = 1.10 × 0.90 − 1 = −1%. Simply comparing the £180,000 ending value with the £100,000 starting value would be meaningless because £90,000 of the increase came from the external deposit.
Thought exercise: why can the investor's money-weighted return be worse than −1% if most of the invested capital was present during the losing sub-period?
Common mistakes and practical workflow
- Treating deposits as investment gains.
- Using arithmetic averages instead of geometric linking.
- Splitting periods for internal trades rather than external flows.
- Assuming TWR represents the investor's realised cash-flow experience.
Practical workflow
- Identify every external cash flow.
- Obtain reliable portfolio valuations around each flow.
- Calculate each sub-period return consistently net or gross of fees.
- Geometrically link the sub-period returns.
- Report TWR alongside cash-flow context and, where useful, money-weighted return.
Knowledge checkpoint
- Why does TWR split at external cash flows?
- How are sub-period returns linked?
- Why is an internal rebalance not an external cash flow?
- What question does money-weighted return answer that TWR does not?
FAQs
❓ Can TWR be negative when the account value rose?
Yes. Deposits can increase account value even when investment performance is negative.
❓ Does TWR ignore cash flows?
No. It neutralises their timing effect by splitting the measurement periods.
❓ Should fees be included?
The report should clearly state whether returns are gross or net and apply that policy consistently.
❓ Is TWR the best measure of my personal return?
Not always. Money-weighted return may better reflect the result of your actual timed contributions and withdrawals.
Summary
Time-weighted return isolates the investment process from external cash-flow timing. Accurate flow data, sub-period valuations and geometric linking are essential, and the result should not be confused with the investor's money-weighted experience.
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