Year	Percent (Units)
1980	0.016
1981	0.016
1982	0.015
1983	0.014
1984	0.013
1985	0.013
1986	0.012
1987	0.010
1988	0.011
1989	0.011
1990	0.010
1991	0.009
1992	0.008
1993	0.008
1994	0.007
1995	0.008
1996	0.008
1997	0.008
1998	0.008
1999	0.008
2000	0.008
2001	0.008
2002	0.008
2003	0.008
2004	0.008
2005	0.008
2006	0.008
2007	0.008
2008	0.008
2009	0.009
2010	0.008
2011	0.009
2012	0.009
2013	0.009
2014	0.009
2015	0.009
2016	0.007
2017	0.009
2018	0.009
2019	0.008
2020	0.007
2021	0.007
2022	0.007
2023	0.007
2024	0.007
2025	0.007
2026	0.007
2027	0.007
2028	0.007
2029	0.007