Year	Percent
1980	0.662
1981	0.68
1982	0.688
1983	0.685
1984	0.684
1985	0.676
1986	0.672
1987	0.668
1988	0.655
1989	0.647
1990	0.627
1991	0.606
1992	0.539
1993	0.519
1994	0.524
1995	0.526
1996	0.515
1997	0.509
1998	0.517
1999	0.522
2000	0.521
2001	0.517
2002	0.513
2003	0.504
2004	0.5
2005	0.49
2006	0.487
2007	0.478
2008	0.462
2009	0.44
2010	0.443
2011	0.437
2012	0.422
2013	0.413
2014	0.41
2015	0.414
2016	0.412
2017	0.406
2018	0.401
2019	0.393
2020	0.386
2021	0.38
2022	0.374
2023	0.368
2024	0.363