Ticket sales for the top 100 acts are down 12 percent for the first six months of 2010, according to Live Nation Entertainment.

The world’s largest concert promoter announced the news on Thursday causing shares of the Los Angeles-based company to plummet. The company further stated things are likely to get much worse before they get better, noting that sales could drop another 15% during the last half of 2010.

Live Nation took its case directly to Wall Street analysts, but midway through the meeting, its shares plummeted more than 16 percent, wiping out some $322 million in market value, according to the AP. The stock recovered somewhat to end the day with an 11 percent decline, down $1.24 at $10.19.

Live Nation CEO Michael Rapino blamed the weak economy. The company’s executive chairman Irving Azoff blamed the shareholders for selling off during a video conference call, remarking that he hoped their dumping stock “isn’t indicative of the fact that we have a group of investors that are so shortsighted” according to Associated Press.

Billboard reported that Azoff also told investors, “If you believe there is going to be a music business…there is no other play than this company.”

Live Nation and Ticketmaster merged earlier this year. Thursday’s 16% stock plunge was the lowest for the company since it announced  the Department of Justice had approved the merger.

Live Nation also revealed that U2’s tour postponement of its summer U.S. leg due to Bono’s back injury alone cost the company $6 million.  The dates have been rescheduled for next summer.