American Association of Individual Investors

American Association of Individual Investors

Understanding the Performance Measurement Enigma

Why the most common method to calculate fund performance does not reflect how most people invest.

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AAII
Oct 07, 2025
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The standard method of measuring the performance of exchange-traded funds (ETFs) and mutual funds is to assume that money was invested all at once (a lump-sum investment) and no additional money was invested or withdrawn. Is that how most people invest? I doubt it. Is there a measure of performance that is more realistic? In this article, I present performance results based on two different assumptions: (1) monthly investments and (2) money withdrawn annually.

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