The popular investing strategy performs well during rising markets, but it lags behind another strategy during down markets.

Here's a breakdown: In this example, even with price fluctuations over the three months, at $300 invested with 17 shares, your average cost per share is $17.65 ($300 ÷ 17 = $17.65). If you were ...

This can help lower your average cost per share over time. Think of it like shopping throughout the year instead of doing all your shopping on a single day: Some days you'll catch sales and get ...

Over time, the strategy should lower your average cost per share, if purchases correspond to market cycles.