Investors may be thrilled about the current bull market, but one market watcher believes that paying attention to volume is a better way to maximize their profit.

Paul Hickey, co-founder of Bespoke Investment Group, took a look at the performance of the S&P 500 Index over the years as it compared to volume. What he found was a huge difference in returns on days with below-average market volume, and on days when it was above-average.

"The cumulative return of the S&P 500 during this bull market on below average volume days [increased] 823 percent," said Hickey Thursday on CNBC's "Futures Now." "Cumulative return of the S&P 500 on above average volume days [saw] a decline of 65 percent."

In other words, "if you're looking to only participate when you have strong volume, you're going to be losing quite a bit of money."

Market volume is a measure of the amount of trading that occurred in a given time period.

Hickey has seen market volume decline over the years, which he largely blames on a stricter regulatory environment curtailing trading at big banks.