What's the most profitable corporation in Sweden?
Wrong, if you said Volvo or Bjorn Borg. It is ABBA, the world's top-selling recording group. But six-year-old ABBA, an acronym for Members Agnetha Faltskog, 31, Bjorn Ulvaeus, 35, Benny Anderson, 34, and Anni-Frid Lyngstad, 35, earns only part of its income from rock 'n' roll. Much of it comes from sidelineslike importing oil, leasing computers, investing in real estate and running one of the largest art galleries in Europe. These and other enterprises, owned by ABBA and its manager Stig Anderson, 50, netted roughly $20 million...