Year	Percent (Units)
1980	0.653
1981	0.669
1982	0.675
1983	0.673
1984	0.673
1985	0.664
1986	0.661
1987	0.658
1988	0.645
1989	0.639
1990	0.619
1991	0.597
1992	0.533
1993	0.513
1994	0.518
1995	0.519
1996	0.508
1997	0.503
1998	0.510
1999	0.514
2000	0.514
2001	0.509
2002	0.506
2003	0.498
2004	0.493
2005	0.484
2006	0.482
2007	0.473
2008	0.458
2009	0.440
2010	0.443
2011	0.440
2012	0.429
2013	0.420
2014	0.416
2015	0.429
2016	0.430
2017	0.432
2018	0.426
2019	0.422
2020	0.425
2021	0.424
2022	0.422
2023	0.408
2024	0.397
2025	0.393
2026	0.389
2027	0.386
2028	0.382
2029	0.379