Year	Percent (Units)
1980	0.660
1981	0.661
1982	0.706
1983	0.751
1984	0.777
1985	0.805
1986	0.816
1987	0.819
1988	0.815
1989	0.810
1990	0.797
1991	0.794
1992	0.717
1993	0.724
1994	0.732
1995	0.738
1996	0.745
1997	0.759
1998	0.794
1999	0.814
2000	0.818
2001	0.827
2002	0.830
2003	0.823
2004	0.814
2005	0.812
2006	0.825
2007	0.839
2008	0.873
2009	0.918
2010	0.917
2011	0.898
2012	1.003
2013	0.986
2014	0.944
2015	1.000
2016	0.959
2017	0.912
2018	0.928
2019	0.953
2020	1.016
2021	0.986
2022	1.018
2023	1.024
2024	1.022
2025	1.035
2026	1.051
2027	1.071
2028	1.096
2029	1.123