Year	Percent (Units)
1980	0.666
1981	0.705
1982	0.651
1983	0.603
1984	0.603
1985	0.567
1986	0.443
1987	0.449
1988	0.418
1989	0.467
1990	0.555
1991	0.553
1992	0.514
1993	0.505
1994	0.527
1995	0.542
1996	0.550
1997	0.574
1998	0.564
1999	0.565
2000	0.606
2001	0.600
2002	0.598
2003	0.625
2004	0.650
2005	0.651
2006	0.680
2007	0.666
2008	0.668
2009	0.636
2010	0.636
2011	0.650
2012	0.643
2013	0.627
2014	0.634
2015	0.554
2016	0.532
2017	0.526
2018	0.515
2019	0.506
2020	0.496
2021	0.486
2022	0.507
2023	0.509
2024	0.511
2025	0.515
2026	0.521
2027	0.527
2028	0.535
2029	0.542