Year	Percent
1980	0.022
1981	0.022
1982	0.022
1983	0.021
1984	0.021
1985	0.019
1986	0.018
1987	0.018
1988	0.017
1989	0.018
1990	0.017
1991	0.015
1992	0.013
1993	0.012
1994	0.012
1995	0.011
1996	0.008
1997	0.006
1998	0.006
1999	0.005
2000	0.005
2001	0.006
2002	0.007
2003	0.008
2004	0.008
2005	0.008
2006	0.008
2007	0.008
2008	0.008
2009	0.008
2010	0.008
2011	0.009
2012	0.01
2013	0.011
2014	0.011
2015	0.009
2016	0.009
2017	0.009
2018	0.009
2019	0.009
2020	0.009
2021	0.01
2022	0.01
2023	0.01
2024	0.01