Year	Percent (Units)
1980	0.020
1981	0.019
1982	0.020
1983	0.021
1984	0.020
1985	0.021
1986	0.020
1987	0.020
1988	0.020
1989	0.020
1990	0.019
1991	0.018
1992	0.015
1993	0.015
1994	0.015
1995	0.015
1996	0.015
1997	0.015
1998	0.016
1999	0.016
2000	0.016
2001	0.016
2002	0.016
2003	0.015
2004	0.015
2005	0.015
2006	0.014
2007	0.014
2008	0.013
2009	0.013
2010	0.012
2011	0.012
2012	0.012
2013	0.011
2014	0.011
2015	0.011
2016	0.011
2017	0.011
2018	0.011
2019	0.011
2020	0.008
2021	0.009
2022	0.010
2023	0.010
2024	0.010
2025	0.010
2026	0.010
2027	0.010
2028	0.010
2029	0.009