Year	Percent (Units)
1980	1.276
1981	1.125
1982	1.066
1983	1.099
1984	1.049
1985	1.052
1986	1.052
1987	1.037
1988	1.025
1989	1.026
1990	0.916
1991	0.831
1992	0.763
1993	0.781
1994	0.798
1995	0.822
1996	0.841
1997	0.865
1998	0.884
1999	0.892
2000	0.888
2001	0.877
2002	0.866
2003	0.861
2004	0.859
2005	0.849
2006	0.856
2007	0.870
2008	0.881
2009	0.910
2010	0.890
2011	0.900
2012	0.890
2013	0.874
2014	0.876
2015	0.909
2016	0.918
2017	0.930
2018	0.952
2019	0.967
2020	0.976
2021	0.981
2022	0.999
2023	0.970
2024	0.970
2025	0.972
2026	0.974
2027	0.973
2028	0.972
2029	0.972