Answer: geometric mean return.

Geometric mean return (time-weighted return) is the most appropriate method for performance measurement as it does not consider additions to or withdrawals from the account. This is particularly important for a buy-and-hold investor making regular deposits because: 1. **Time-weighted return (geometric mean)** eliminates the impact of cash flows (deposits/withdrawals), allowing for fair comparison of investment manager performance. 2. **Money-weighted return (internal rate of return)** is affected by the timing and size of cash flows, making it inappropriate for evaluating portfolio performance when the investor controls the timing of deposits. 3. **Arithmetic mean return** is a simple average that doesn't account for compounding effects and is less suitable for multi-period performance evaluation. For a buy-and-hold strategy with regular deposits, the geometric mean provides the most accurate measure of the portfolio's compound growth rate over time, independent of the investor's deposit schedule.

Author: LeetQuiz Editorial Team