Year	Percent (Units)
1980	0.018
1981	0.019
1982	0.019
1983	0.018
1984	0.018
1985	0.018
1986	0.019
1987	0.020
1988	0.019
1989	0.018
1990	0.018
1991	0.017
1992	0.015
1993	0.015
1994	0.015
1995	0.014
1996	0.015
1997	0.015
1998	0.015
1999	0.015
2000	0.016
2001	0.016
2002	0.015
2003	0.015
2004	0.015
2005	0.016
2006	0.016
2007	0.016
2008	0.016
2009	0.015
2010	0.014
2011	0.014
2012	0.013
2013	0.014
2014	0.014
2015	0.015
2016	0.015
2017	0.016
2018	0.016
2019	0.016
2020	0.015
2021	0.015
2022	0.016
2023	0.016
2024	0.016
2025	0.015
2026	0.015
2027	0.015
2028	0.015
2029	0.015