Year Percent (Units) 1980 0.002 1981 0.002 1982 0.002 1983 0.002 1984 0.002 1985 0.002 1986 0.002 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 0.004 2003 0.004 2004 0.004 2005 0.004 2006 0.004 2007 0.004 2008 0.005 2009 0.005 2010 0.005 2011 0.005 2012 0.006 2013 0.006 2014 0.006 2015 0.006 2016 0.007 2017 0.007 2018 0.007 2019 0.007 2020 0.007 2021 0.006 2022 0.006 2023 0.007 2024 0.007 2025 0.007 2026 0.007 2027 0.007 2028 0.007 2029 0.007