A recent CFA Institute article suggests that the concept of the competitive moat—made famous by legendary investor Warren Buffett—is murky and tough to gauge and we should instead focus on the more measurable concept of market power.

The article reports that while many have tried to drill down on what exactly Buffett means by a moat, there really is no way to measure the idea: “It is a qualitative metric that is impossible to gauge in most instances.” Instead, it suggests, maybe we should measure a firm’s market power, a metric explored in a recent study that examined whether “companies whose products have fewer competitors have an advantage.”

The study, which used a database of product competition between U.S. companies, found that firms with less competition tend to be older, have higher share valuations and lower liquidity and are followed by fewer analysts. “In short,” the article notes, “they are mostly small- to medium-sized firms that operate in small market niches where a few highly specialized companies compete with each other.”

While these factors should position companies with fewer competitors for higher share price returns in the long run, the study found that (from 1999 to 2017), companies with less market power had nearly the same returns as their high-market-power peers. The study also found, however, that fund managers who invested in higher market power firms outperformed the average actively managed fund by 1.56% per year.

How is that possible? “The trick is,” the article notes, “that market power isn’t stable. The number of competitor products changes all the time.” And since fund managers tend to invest in companies with rising market power (and sell those whose market power may be dipping), they are effectively “investing in companies that operate in less efficient markets with fewer competitors and thus have the ability to gain a larger share of the market and increase their profit margins. And this creates an advantage for the fund manager independent of the fund style.”

The article concludes by suggesting that those fund managers who take market power into account—typically the older and more experienced of the bunch—have probably “learned in their careers to focus less on talk about moats and other murky and ephemeral concepts and instead concentrate on how close a company is to holding a monopoly in its particular niche.”