Year Percent (Units) 1980 0.008 1981 0.008 1982 0.008 1983 0.008 1984 0.008 1985 0.007 1986 0.009 1987 0.009 1988 0.009 1989 0.010 1990 0.010 1991 0.010 1992 0.010 1993 0.010 1994 0.010 1995 0.010 1996 0.010 1997 0.010 1998 0.010 1999 0.010 2000 0.009 2001 0.009 2002 0.009 2003 0.009 2004 0.009 2005 0.009 2006 0.009 2007 0.009 2008 0.009 2009 0.009 2010 0.009 2011 0.009 2012 0.009 2013 0.009 2014 0.009 2015 0.009 2016 0.008 2017 0.008 2018 0.008 2019 0.008 2020 0.008 2021 0.008 2022 0.008 2023 0.008 2024 0.008 2025 0.008 2026 0.008 2027 0.008 2028 0.008 2029 0.008