Toxic singer Britney Spears is worth $120 million to the U.S. economy, according to big business magazine Portfolio. After an exhaustive study, the magazine has published statistics that make the troubled star a pop culture icon and a boost to American finances.Portfolio reports that between January 2006 and July 2007, Spears appeared on the front covers of the leading U.S. tabloids 175 times in 78 weeks, and she has been the number one search subject on website Yahoo! in six of the past seven years.The magazine also discovered that a Las Vegas nightclub reportedly sold seats next to Spears’ table for $50,000 and the pop star can still earn as much as $400,000 in appearance fees.The publication also estimates Spears makes a personal fortune of $9 million a year, and despite her reported financial woes, has a personal fortune of about $125 million.