Year Percent 1991-01-01 52.0724 1992-01-01 49.1855 1993-01-01 21.1110 1994-01-01 14.9819 1995-01-01 13.9301 1996-01-01 17.0439 1997-01-01 18.6642 1998-01-01 18.1365 1999-01-01 14.4891 2000-01-01 13.8685 2001-01-01 16.4079 2002-01-01 19.0354 2003-01-01 21.2039 2004-01-01 23.1447 2005-01-01 24.9281 2006-01-01 27.7454 2007-01-01 33.0843 2008-01-01 37.4447 2009-01-01 40.2949 2010-01-01 36.7374 2011-01-01 36.1981 2012-01-01 40.1662 2013-01-01 42.3627 2014-01-01 40.5218 2015-01-01 37.0849 2016-01-01 32.5564