Year Percent 1991-01-01 33.871700000000000 1992-01-01 36.863500000000000 1993-01-01 41.131500000000000 1994-01-01 41.992200000000000 1995-01-01 39.491700000000000 1996-01-01 36.301600000000000 1997-01-01 31.996200000000000 1998-01-01 25.814700000000000 1999-01-01 25.814700000000000 2000-01-01 20.716500000000000 2001-01-01 17.173400000000000 2002-01-01 20.851600000000000 2003-01-01 31.850200000000000 2004-01-01 32.465800000000000 2005-01-01 29.519900000000000 2006-01-01 25.676300000000000 2007-01-01 26.123600000000000 2008-01-01 30.621500000000000 2009-01-01 22.817100000000000 2010-01-01 21.943200000000000 2011-01-01 30.451999999999998 2012-01-01 38.205200000000000 2013-01-01 45.837200000000000 2014-01-01 51.819700000000000 2015-01-01 54.841800000000000 2016-01-01 55.008999999999990