Year Percent 1996-01-01 29.875999999999998 1997-01-01 33.944900000000000 1998-01-01 32.262200000000000 1999-01-01 32.465600000000000 2000-01-01 32.324700000000000 2001-01-01 35.191700000000000 2002-01-01 40.163700000000000 2003-01-01 45.956600000000000 2004-01-01 45.718000000000000 2005-01-01 46.403700000000000 2006-01-01 43.816700000000000 2007-01-01 41.645300000000000 2008-01-01 40.578600000000000 2009-01-01 42.324800000000000 2010-01-01 46.403500000000000 2011-01-01 43.455900000000000 2012-01-01 46.141400000000000 2013-01-01 47.766100000000000 2014-01-01 49.589700000000000 2015-01-01 51.830600000000000 2016-01-01 52.446500000000000