Year Percent 1990 3.41029 1991 3.82698 1992 3.74199 1993 3.68028 1994 3.57739 1995 2.98696 1996 3.05071 1997 3.02042 1998 3.07393 1999 3.03989 2000 3.00641 2001 2.96 2002 2.91789 2003 2.91658 2004 2.87665 2005 2.84805 2006 2.81161 2007 2.78089 2008 2.76057 2009 2.62841 2010 2.59444 2011 2.54919 2012 2.51053 2013 2.47612 2014 2.30944 2015 2.28334 2016 2.26091 2017 2.23636 2018 2.13229 2019 2.12782 2020 1.98971