Mutual Fund Returns with Dividends and Dietz Timing Adjustment

Summary

The note explains how to calculate a mutual fund's periodic return from its beginning and ending net asset values and a dividend. When the dividend is paid at the period end, adding it to the ending value gives the standard total return calculation. If the payment date within the period is unknown, treating it as an end-period cash flow introduces a small timing error.

The direction of that error depends on price movement: with a rising NAV, the basic calculation understates return; with a falling NAV, it overstates it. The Simple Dietz method approximates a mid-period dividend by adjusting the denominator for half the distribution. The response suggests this refinement may be unnecessary for monthly or weekly data, and notes that fund dividends often arrive late in the month. That timing observation is experience-based rather than demonstrated with data in the note.

Key ideas

• For a dividend paid at period end, include it with the ending NAV when calculating total return.
• An unknown dividend date creates a timing approximation in periodic return calculations.
• An end-period assumption understates returns when NAV rises and overstates them when NAV falls.
• The Simple Dietz method approximates a mid-period distribution through a denominator adjustment.
• The correction may be immaterial for monthly or weekly observations, depending on the use case.

Tags

# Calculating Mutual Fund Returns


# Calculating Mutual Fund Returns












Using Thomson Reuters Eikon I can extract the monthly NAV and Dividen Payments of a fund. I would like to calculate the monthly returns of a fund now. Would this be the right approach?

## Fund Date NAV Div

```
1       1       10   -
1       2       11    1
```

Return = (11+1)/10 -1 = 0.2 = 20%

## Answer by Alex C (score 1)

https://quant.stackexchange.com/a/41592

If the dividend is received on the last day of the month then your approach $r=\frac{P_{t-1}-P_t+D}{P_{t-1}}$ is perfectly correct.

If the dividend is received at some unknown time during the month, then a minor error is introduced: the return is underestimated when the price is rising and overestimated when the price is falling. With monthly (or weekly) data this error is probably too small to worry about.

The Simple Dietz Method, which assumes that the dividend is received half-way in the month, proposes the formula $r=\frac{P_{t-1}-P_t+D}{P_{t-1}-D/2}$. As I said, this correction is probably unnecessary in your case. In my experience BTW mutual fund dividends do tend to occur in the latter part (days 20-31) of the month.

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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.