Year	Percent (Units)
1980	0.025
1981	0.023
1982	0.023
1983	0.024
1984	0.024
1985	0.024
1986	0.023
1987	0.023
1988	0.022
1989	0.022
1990	0.022
1991	0.024
1992	0.020
1993	0.021
1994	0.018
1995	0.020
1996	0.021
1997	0.022
1998	0.022
1999	0.022
2000	0.021
2001	0.019
2002	0.019
2003	0.020
2004	0.020
2005	0.019
2006	0.019
2007	0.020
2008	0.021
2009	0.023
2010	0.023
2011	0.023
2012	0.022
2013	0.023
2014	0.023
2015	0.022
2016	0.022
2017	0.021
2018	0.021
2019	0.022
2020	0.023
2021	0.022
2022	0.022
2023	0.022
2024	0.022
2025	0.022
2026	0.022
2027	0.022
2028	0.023
2029	0.023