Online dating is more popular than ever, with millions of people hoping that dating sites will find them a perfect match. But new research has found one flaw in the way people think about dating sites.

A study by Northwestern University researchers published in the journal Psychological Science in the Public Interest has thrown light on the efficacy of dating sites, according to the Washington Post. The research found that while dating sites are very helpful in getting users to meet more people, the algorithms that they claim can help find your mate are actually little better than chance in arranging lasting relationships.

The Northwestern team suggests that dating sites are guilty of false advertising by promises that suggest they will lead users to life partners. They have urged the Federal Communications Commission to investigate and clamp down on the industry’s claims.

The study suggests that successful relationships rely on three factors. Individual characteristics are first, including intelligence or the kinds of relationships partners tend to favor. Next is whether partners enjoy their initial interactions. Finally, circumstances that matter to each partner, like race or health, also come into play.

But dating algorithms cannot predict the effects of these areas, especially when it comes to potential future circumstances. They also cannot possibly account for the wide range of potential outcomes from the time a couple first meets through the course of even a relationship of a few weeks.

Given these limitations, dating sites’ algorithms tend to focus on matching personalities, putting people together with similar partners. But studies of successful marriages, for example, show that having similar personalities accounts for only half of one percent of how happy they are.

In short, the researchers say that dating site users should look skeptically at any claims made about matching for long term relationship success, but instead rely on the sites only for the purpose of meeting more people.