Year	Percent (Units)
1980	0.019
1981	0.019
1982	0.019
1983	0.019
1984	0.018
1985	0.020
1986	0.020
1987	0.020
1988	0.020
1989	0.020
1990	0.019
1991	0.020
1992	0.018
1993	0.018
1994	0.018
1995	0.018
1996	0.020
1997	0.020
1998	0.021
1999	0.022
2000	0.021
2001	0.022
2002	0.022
2003	0.023
2004	0.023
2005	0.024
2006	0.024
2007	0.024
2008	0.024
2009	0.025
2010	0.026
2011	0.027
2012	0.027
2013	0.027
2014	0.027
2015	0.028
2016	0.030
2017	0.032
2018	0.033
2019	0.034
2020	0.035
2021	0.036
2022	0.035
2023	0.035
2024	0.036
2025	0.037
2026	0.038
2027	0.038
2028	0.039
2029	0.040