Justin Bieber passed Lady Gaga earlier this year to become the Twitter user with the most followers on the microblogging site, but a new study suggests more than half of the pop star’s 37.3 million followers are fake accounts, according to the BBC(Opens in a new window).

Social network tracker SocialBakers found that just 17.8 million of Bieber’s followers were “genuine fans” linked to real accounts, or 47 percent of his total, the news organization reported. SocialBakers states that its methodology for determining “fake followers”(Opens in a new window) is to look for the following:

• The account is following less than 50 people and has less than one follower
• More than 30 percent of all tweets use spam phrases, such as “diet,” “make money,” and “work from home”
• The same tweets are repeated more than three times, even when posted to different accounts
• More than 90 percent of the account´s tweets are retweets
• More than 90 percent of tweets are links and the profile has a following: followers ratio of 7: 1 or more. This means the profile is following seven users while only being followed by one.
• The account has never tweeted
• The account is more than two months old and still has a default profile image

SocialBakers, which sells an app to block fake followers, concedes that its criteria for sniffing out bogus accounts isn’t perfect, but argues that “these kinds of followers can be considered empty or inactive and therefore not helpful to you in terms of reach.”

Bieber made news in January when he overtook fellow pop idol Lady Gaga(Opens in a new window) on Twitter—Gaga herself took her dethroning well, firing off a congratulatory tweet(Opens in a new window) to the teen singing sensation.

He also made Twitter news in 2012. The microblogging site pegged Bieber’s goodbye tweet(Opens in a new window) to a six-year-old fan who died of brain cancer as the second-most re-tweeted message of the year, behind only President Barack Obama’s election night “Four more years” victory tweet featuring a photo of him hugging First Lady Michelle Obama.