Summer's over, but recent trends in sunbathing suggest those tans may not be so quick to fade. According to Chicago-based market research firm Mintel, the indoor tanning industry raked in 4.2 billion in 2000, up from $4 billion in 1999. And there's no shortage of UV rays to go around. In addition to the estimated 15,000 locations in the United States that offer indoor tanning exclusively, another 12,000 to 15,000 locations such as health clubs and beauty salons also provide year-round indoor tanning. For comparison's sake, the state of Florida has 192 beaches.