Year Percent 1991-01-01 16.2162 1992-01-01 15.7365 1993-01-01 23.9132 1994-01-01 29.0901 1995-01-01 31.1271 1996-01-01 27.0912 1997-01-01 22.7462 1998-01-01 24.2783 1999-01-01 24.3833 2000-01-01 20.8914 2001-01-01 18.4202 2002-01-01 15.0466 2003-01-01 13.6991 2004-01-01 14.7752 2005-01-01 16.0011 2006-01-01 22.4404 2007-01-01 23.0931 2008-01-01 22.8078 2009-01-01 28.6840 2010-01-01 26.4045 2011-01-01 25.3825 2012-01-01 28.0117 2013-01-01 31.4511 2014-01-01 27.6817 2015-01-01 28.2181 2016-01-01 24.8058