Year Percent 1990 2.10963 1991 1.46325 1992 1.06518 1993 1.03462 1994 0.93564 1995 0.77594 1996 1.05796 1997 1.02016 1998 0.9849 1999 0.89833 2000 0.8714 2001 0.84629 2002 0.71986 2003 0.70023 2004 0.68139 2005 0.66266 2006 0.64382 2007 0.62534 2008 0.52056 2009 0.50561 2010 0.49126 2011 0.47755 2012 0.46457 2013 0.45234 2014 0.44076 2015 0.43095 2016 0.42163 2017 0.41266 2018 0.40616 2019 0.40001 2020 0.39964