Year Number 2004-01-01 3.9745 2005-01-01 4.1447 2006-01-01 5.6337 2007-01-01 6.4582 2008-01-01 10.3567 2009-01-01 12.0561 2010-01-01 10.8824 2011-01-01 11.7492 2012-01-01 13.6633 2013-01-01 14.7722 2014-01-01 15.6566 2015-01-01 15.3707