Year	Percent (Units)
1980	0.021
1981	0.021
1982	0.021
1983	0.020
1984	0.020
1985	0.018
1986	0.017
1987	0.017
1988	0.016
1989	0.017
1990	0.016
1991	0.015
1992	0.012
1993	0.012
1994	0.012
1995	0.010
1996	0.007
1997	0.006
1998	0.006
1999	0.005
2000	0.005
2001	0.006
2002	0.007
2003	0.007
2004	0.007
2005	0.007
2006	0.007
2007	0.008
2008	0.008
2009	0.008
2010	0.008
2011	0.008
2012	0.009
2013	0.011
2014	0.011
2015	0.010
2016	0.011
2017	0.010
2018	0.010
2019	0.010
2020	0.010
2021	0.010
2022	0.010
2023	0.010
2024	0.010
2025	0.010
2026	0.010
2027	0.011
2028	0.011
2029	0.011