Year	Percent (Units)
1980	1.286
1981	1.187
1982	1.146
1983	1.160
1984	1.133
1985	1.018
1986	1.054
1987	1.042
1988	0.977
1989	0.876
1990	0.831
1991	0.896
1992	0.890
1993	0.928
1994	0.954
1995	0.894
1996	0.908
1997	0.943
1998	0.953
1999	0.890
2000	0.842
2001	0.786
2002	0.681
2003	0.713
2004	0.738
2005	0.767
2006	0.788
2007	0.816
2008	0.825
2009	0.779
2010	0.815
2011	0.832
2012	0.812
2013	0.802
2014	0.764
2015	0.773
2016	0.760
2017	0.847
2018	0.797
2019	0.760
2020	0.705
2021	0.733
2022	0.745
2023	0.711
2024	0.670
2025	0.682
2026	0.691
2027	0.696
2028	0.697
2029	0.692