Year	Percent (Units)
1980	0.851
1981	0.846
1982	0.832
1983	0.817
1984	0.807
1985	0.808
1986	0.795
1987	0.778
1988	0.768
1989	0.774
1990	0.772
1991	0.746
1992	0.671
1993	0.657
1994	0.646
1995	0.627
1996	0.606
1997	0.596
1998	0.597
1999	0.586
2000	0.582
2001	0.578
2002	0.562
2003	0.539
2004	0.525
2005	0.516
2006	0.511
2007	0.504
2008	0.503
2009	0.493
2010	0.484
2011	0.475
2012	0.471
2013	0.471
2014	0.473
2015	0.482
2016	0.484
2017	0.473
2018	0.470
2019	0.462
2020	0.465
2021	0.461
2022	0.458
2023	0.448
2024	0.440
2025	0.432
2026	0.426
2027	0.419
2028	0.413
2029	0.406