Year	Percent (Units)
1980	0.849
1981	0.833
1982	0.862
1983	0.892
1984	0.905
1985	0.873
1986	0.864
1987	0.839
1988	0.799
1989	0.726
1990	0.659
1991	0.560
1992	0.460
1993	0.458
1994	0.462
1995	0.478
1996	0.478
1997	0.432
1998	0.400
1999	0.382
2000	0.375
2001	0.385
2002	0.396
2003	0.390
2004	0.409
2005	0.408
2006	0.419
2007	0.427
2008	0.453
2009	0.430
2010	0.393
2011	0.395
2012	0.394
2013	0.371
2014	0.374
2015	0.382
2016	0.404
2017	0.433
2018	0.443
2019	0.448
2020	0.444
2021	0.441
2022	0.446
2023	0.442
2024	0.441
2025	0.442
2026	0.445
2027	0.449
2028	0.451
2029	0.453