Year	Percent
1980	0.311
1981	0.323
1982	0.332
1983	0.339
1984	0.338
1985	0.339
1986	0.34
1987	0.337
1988	0.33
1989	0.332
1990	0.334
1991	0.34
1992	0.32
1993	0.327
1994	0.332
1995	0.336
1996	0.34
1997	0.344
1998	0.352
1999	0.358
2000	0.361
2001	0.37
2002	0.377
2003	0.383
2004	0.386
2005	0.391
2006	0.397
2007	0.401
2008	0.411
2009	0.435
2010	0.438
2011	0.448
2012	0.461
2013	0.473
2014	0.486
2015	0.503
2016	0.522
2017	0.542
2018	0.563
2019	0.586
2020	0.605
2021	0.625
2022	0.646
2023	0.667
2024	0.689