Year Percent 1990 0.2 1991 0.17 1992 0.2 1993 0.2 1994 0.25 1996 0.27 1997 0.38 1998 0.47 1999 0.51 2000 0.42 2001 1.12 2002 1.19 2003 1.63 2004 1.52 2005 0.93 2006 0.98 2007 1.15 2008 0.81 2009 0.95 2010 1.21 2011 0.89 2012 0.78 2013 0.71 2014 0.67 2015 0.66 2016 0.68 2017 0.71 2018 0.8 2019 0.53 2020 0.98