Year	Percent
1980	0.656
1981	0.664
1982	0.704
1983	0.724
1984	0.732
1985	0.746
1986	0.72
1987	0.688
1988	0.646
1989	0.653
1990	0.632
1991	0.61
1992	0.557
1993	0.535
1994	0.515
1995	0.515
1996	0.516
1997	0.501
1998	0.512
1999	0.511
2000	0.506
2001	0.509
2002	0.522
2003	0.538
2004	0.533
2005	0.539
2006	0.52
2007	0.51
2008	0.507
2009	0.518
2010	0.51
2011	0.503
2012	0.504
2013	0.502
2014	0.503
2015	0.505
2016	0.505
2017	0.493
2018	0.486
2019	0.482
2020	0.474
2021	0.464
2022	0.453
2023	0.439
2024	0.425