Was TISL cd sales helped by the many female singer guest appearances?

[mikephxaz]

I'm one of those crazy obsessed fans that bought Vanessa'sCarlton's album because Stevie did the duet..I also bought Tom Petty's releases because of Stevie's vocals on The Insider, Needles and Pins and etc.....Is there a chance that Natalie Maines(Dixie Chicks) Sheryl Crow, Macy Gray and Sarah's appearances on Trouble in Shangri La could have given Stevie's sales an additional 20% in sales.....possible??? What would have happened if Taylor Swift would have done the harmonies on For Whats Its Worth, Tom Petty had done Everybody Love You duet with her and Sheryl had done the harmonies for You Might Be The One and Annie Lennox had done the back up vocals on Moonlight.and Courtney Love had done back up vocals for Ghosts are Gone ...would that had sold another 30,000 units the first week?...just a thought