According to Billboard.com, METALLICA's self-titled 1991 album should surpass 16 million copies sold in the U.S., according to Nielsen SoundScan, in about three or four months at its current rate of sales (about 2,000 to 3,000 per week).The set — often referred to as "the black album" — was already certified 16 times platinum on December 13, 2012 by the RIAA (Recording Industry Association Of America) for shipments in excess of 16 million copies in the U.S. "Metallica" in 2009 surpassed SHANIA TWAIN's 1997 record, "Come On Over", as the best-selling CD of the SoundScan era. Although METALLICA had scored their first radio and video airplay with their previous effort, 1988's "...And Justice For All", the black album was the band's biggest commercial breakthrough, producing five singles and making them into one of the most popular rock bands in the world. Drummer Lars Ulrich told Rolling Stone in 1991 about the record's musical shift, "We felt inadequate as musicians and as songwriters (early in our career). That made us go too far, around 'Master Of Puppets' and on '...And Justice For All', in the direction of trying to prove ourselves. We'll do all this weird-ass shit sideways to prove that we are capable musicians and songwriters." Ulrich added about the eight months it took to make the album, "[Recording] should have gone quicker, in theory, than trying to get everything note-perfect like we have before. But as usual with METALLICA, all those theories and normalities go straight out the window. It took us twice as long to make a record that is twice as loose." Frontman James Hetfield said, "It was [once] a challenge for us to jam every riff in the universe into one song and make it work. Now we're pretty much doing the opposite. Which is even more of a challenge." The album was the first of four collaborations with producer Bob Rock, with whom the band clashed throughout the recording of the disc. Rock recalled to Music Radar, "The first three months were difficult. They were all very suspicious of me. It wasn't a fun, easy record to make. I told the guys when we were done that I'd never work with them again. They felt the same way about me." Ulrich said about Rock in NME, "We'd never really had anybody push us before . . . We've always thought of ourselves as 'Big Bad Metallica,' but Bob taught us a new word none of us had ever heard before: soulful." METALLICA performed "the black album" in its entirety at a number of European festivals in 2012.