Year Percent 2001-01-01 3.33 2002-01-01 5.57 2003-01-01 7.38 2004-01-01 6.11 2005-01-01 7.53 2006-01-01 7.86 2007-01-01 8.36 2008-01-01 8.28 2009-01-01 9.67 2010-01-01 7.90 2011-01-01 8.45 2012-01-01 9.14 2013-01-01 10.58 2014-01-01 11.56 2015-01-01 16.56 2016-01-01 17.64