Year	Percent (Units)
1980	0.631
1981	0.618
1982	0.627
1983	0.629
1984	0.605
1985	0.597
1986	0.590
1987	0.578
1988	0.559
1989	0.560
1990	0.561
1991	0.567
1992	0.521
1993	0.514
1994	0.511
1995	0.506
1996	0.499
1997	0.490
1998	0.493
1999	0.494
2000	0.487
2001	0.481
2002	0.476
2003	0.462
2004	0.451
2005	0.440
2006	0.433
2007	0.426
2008	0.420
2009	0.406
2010	0.393
2011	0.389
2012	0.388
2013	0.384
2014	0.380
2015	0.384
2016	0.395
2017	0.391
2018	0.386
2019	0.382
2020	0.367
2021	0.359
2022	0.364
2023	0.351
2024	0.342
2025	0.336
2026	0.331
2027	0.324
2028	0.317
2029	0.310