Year Percent 1980 0.004 1981 0.003 1982 0.004 1983 0.003 1984 0.003 1985 0.003 1986 0.003 1987 0.003 1988 0.003 1989 0.003 1990 0.003 1991 0.003 1992 0.003 1993 0.003 1994 0.003 1995 0.003 1996 0.003 1997 0.003 1998 0.003 1999 0.003 2000 0.003 2001 0.003 2002 0.003 2003 0.002 2004 0.002 2005 0.002 2006 0.002 2007 0.002 2008 0.002 2009 0.002 2010 0.002 2011 0.002 2012 0.002 2013 0.002 2014 0.002 2015 0.002 2016 0.002 2017 0.002 2018 0.002 2019 0.003 2020 0.003 2021 0.003 2022 0.003 2023 0.003 2024 0.003