Year	Percent
1980	0.048
1981	0.048
1982	0.047
1983	0.045
1984	0.043
1985	0.042
1986	0.04
1987	0.039
1988	0.037
1989	0.036
1990	0.034
1991	0.034
1992	0.03
1993	0.028
1994	0.024
1995	0.025
1996	0.025
1997	0.025
1998	0.025
1999	0.025
2000	0.024
2001	0.023
2002	0.022
2003	0.021
2004	0.02
2005	0.019
2006	0.018
2007	0.018
2008	0.018
2009	0.018
2010	0.016
2011	0.017
2012	0.017
2013	0.017
2014	0.017
2015	0.016
2016	0.016
2017	0.016
2018	0.015
2019	0.015
2020	0.015
2021	0.014
2022	0.014
2023	0.014
2024	0.014