Madonna is an American singer, songwriter, actress, and businesswoman. Referred to as the "Queen of Pop" since the 1980s, Madonna is known for pushing the boundaries of lyrical content in mainstream popular music, as well as visual imagery in music videos and on stage. She has also frequently reinvented both her music and image while maintaining autonomy within the recording industry. Besides sparking controversy, her works have been praised by music critics. Madonna is often cited as an influence by other artists. Having sold more than 300 million records worldwide, Madonna is recognized as the best-selling female recording artist of all time by Guinness World Records. The Recording Industry Association of America (RIAA) listed her as the second highest-certified female artist in the U.S., with 64.5 million album units. According to Billboard, Madonna is the most successful solo act on its Hot 100 singles chart and second overall behind the Beatles. She is also the highest-grossing solo touring artist of all time, earning U.S. $1.4 billion from her concert tickets. Inducted into the Rock and Roll Hall of Fame in her first year of eligibility, Madonna topped VH1's countdown of 100 Greatest Women in Music. Additionally, Rolling Stone listed her among the 100 Greatest Artists of All Time and the 100 Greatest Songwriters of All Time.