Year	Percent (Units)
1980	0.024
1981	0.023
1982	0.024
1983	0.024
1984	0.023
1985	0.023
1986	0.023
1987	0.023
1988	0.022
1989	0.021
1990	0.020
1991	0.021
1992	0.022
1993	0.024
1994	0.026
1995	0.024
1996	0.025
1997	0.022
1998	0.023
1999	0.022
2000	0.021
2001	0.020
2002	0.020
2003	0.021
2004	0.020
2005	0.020
2006	0.019
2007	0.020
2008	0.019
2009	0.020
2010	0.021
2011	0.021
2012	0.021
2013	0.021
2014	0.024
2015	0.025
2016	0.026
2017	0.026
2018	0.025
2019	0.025
2020	0.025
2021	0.023
2022	0.024
2023	0.024
2024	0.024
2025	0.024
2026	0.024
2027	0.024
2028	0.024
2029	0.024