Some Justin Bieber fans seem to be concealing their love for the pop superstar.

In a study carried out by the ticketing company Ticketbis, 21 percent of the 21-year-old's fans wouldn't publicly admit to liking his music, according to NME.

Despite the study revealing a portion of Bieber's fans are hiding their devotion to him, it also uncovered that the singer has attracted 10 percent more fans in the U.K. than he had two years ago. The study found that he is the most popular with the 18-30 age range as well.

The study also broke down the singer's fans by city. Southhampton was dubbed the area most likely to have secret Bieber fans with 33 percent. Other cities surveyed were Norwich (28 percent), Edinburgh (28 percent), Newcastle (27 percent), Glasgow (24 percent), Birmingham (23 percent), Leeds (22 percent), Nottingham (21 percent), Manchester (20 percent) and Liverpool (19 percent).

Bieber will head out on the European leg of his Purpose World Tour in the fall next year. He will kick off the trek on Sept. 9 in Kopavogur, Iceland at the Korinn and will wrap up this leg on Nov. 29 at London's O2 Arena.

The "What Do You Mean?" singer will start his North American trek on March 9 at Seattle's KeyArena. From there, he will visit Vancouver, Portland, Sacramento, San Jose, Oakland, Los Angles, Las Vegas, Fresno, San Diego, Glendale, Salt Lake City, Denver, Kansas City, Tulsa, Houston, Dallas, Atlanta, St. Louis, Louisville, Rosemont, Auburn Hills, Cleveland, Columbus, Washington, D.C., Brooklyn, Philadelphia, Boston, Ottawa, Quebec City, Montreal, Toronto, Winnipeg, Calgary, Edmonton, Saskatoon, Fargo, Minneapolis, Lincoln, Des Monies, Cincinnati, Indianapolis, Nashville, Jacksonville, Orlando, Miami, Greensboro, Baltimore, Newark, Hartford, Buffalo, Pittsburgh, and Atlantic City, before he will close out in New York on July 19 at Madison Square Garden.

Bieber released his fourth studio album, "Purpose," on Nov. 13. The album, which topped the U.S. Billboard 200, so far has produced the singles "Sorry," "Love Yourself" and "What Do You Mean?"