Year Percent 1991-01-01 47.372200000000000 1992-01-01 35.166800000000000 1993-01-01 12.890600000000000 1994-01-01 9.855760000000000 1995-01-01 6.402500000000000 1996-01-01 8.454880000000001 1997-01-01 8.116700000000000 1998-01-01 9.886020000000000 1999-01-01 9.986260000000001 2000-01-01 9.263010000000001 2001-01-01 9.942070000000000 2002-01-01 12.506900000000000 2003-01-01 18.349600000000000 2004-01-01 21.365800000000000 2005-01-01 22.616500000000000 2006-01-01 22.629100000000000 2007-01-01 26.473500000000000 2008-01-01 27.028400000000000 2009-01-01 31.734600000000000 2010-01-01 31.948700000000000 2011-01-01 35.860600000000000 2012-01-01 43.152100000000000 2013-01-01 55.178600000000000 2014-01-01 64.526600000000000 2015-01-01 65.836600000000000 2016-01-01 66.622200000000000