Americans lost about $49.3 billion in 2006 to criminals who stole their identities, an 11.5 percent decline that may reflect increased vigilance among consumers and businesses, a study released on Thursday shows. <A HREF="http://www.eweek.com/article2/0,1895,2089404,00.asp?kc=EWWKNEMNL020207EOAD">Losses declined from a revised $55.7 billion in 2005,</A> according to the third annual study by Javelin Strategy & Research. They had increased in each of the prior two years.