The Joshua Tree is the band’s best-selling album, and with 25 million copies sold worldwide, it is among the best-selling albums worldwide. It ranks as one of the best-selling albums in the US. In 1995, the RIAA certified it 10× platinum for shipping 10 million units, and the album subsequently received the Diamond Award for reaching this level.Similarly, the Canadian Recording Industry Association certified the album diamond in Canada. In the UK, it is certified 6× platinum, with an additional silver certification for the 20th anniversary edition.In the Pacific, it is certified 5× platinum and 14× platinum in Australia and New Zealand, respectively.Writer Derek White conducted a mathematical study of The Edge’s rhythmic delay guitar effect in an attempt to explain why his playing style on the record sounded so appealing to him. For a given song, White found that by dividing the number of repeated delay notes per minute by the song’s tempo in beats per minute, he arrived at e, an important mathematical constant that is used to explain many natural phenomena.The Joshua Tree is acclaimed as one of the greatest albums in rock history, and many publications have placed it among their rankings of the best records, including Hot Press, Time, Q, and Entertainment Weekly.  In 1997, The Guardian collated worldwide data in 1997 from a range of renowned critics, artists, and radio DJs, who placed the record at number 57 in the list of the “100 Best Albums Ever”.Rolling Stone magazine ranked the album at number 26 on their 2003 list of “The 500 Greatest Albums of All Time”, writing that U2 “immerse itself in the mythology of the United States” and that “while many of these songs are about spiritual quests… U2 fortify the solemnity with the outright joys of rock & roll”. It was U2’s best position on the list. In 2010, the album appeared at number 62 on Spin’s list of the 125 most influential albums in the 25 years since the magazine launched. The publication said, “The band’s fifth album spit out hits like crazy, and they were unusually searching hits, each with a pointed political edge.”  The band’s penchant for addressing political and social issues, as well as their staid depiction in Corbijn’s black-and-white sleeve photographs, contributed to the group’s earnest and serious image as “stone-faced pilgrim[s]”. This image became a target for derision after the band’s critically maligned Rattle and Hum project in 1988. Various critics called them “po-faced”,  “pompous bores”,  and “humourless”. The group’s continued exploration of American music for the project was labelled “pretentious” and “misguided and bombastic”.  After Bono told fans on the 1989 Lovetown Tour that U2 would “dream it all up again”, the band reinvented themselves in the 1990s. The group incorporated alternative rock, industrial, and electronic dance music into their sound, and adopted a more self-deprecating, flippant image by which they embraced the “rock star” identity they struggled with in the 1980s. The band referred to their 1991 album Achtung Baby as “chopping down the Joshua Tree”. Bill Flanagan summarised the impact of The Joshua Tree on the group’s career in his liner notes to the album’s 20th anniversary release: “The Joshua Tree made U2 into international rock stars and established both a standard they would always have to live up to and an image they would forever try to live down.