Year	Percent (Units)
1980	1.230
1981	1.198
1982	1.179
1983	1.171
1984	1.156
1985	1.146
1986	1.142
1987	1.121
1988	1.122
1989	1.130
1990	1.132
1991	1.132
1992	1.035
1993	1.028
1994	1.029
1995	1.020
1996	1.016
1997	1.019
1998	1.038
1999	1.053
2000	1.047
2001	1.046
2002	1.020
2003	0.982
2004	0.951
2005	0.927
2006	0.911
2007	0.898
2008	0.891
2009	0.862
2010	0.830
2011	0.812
2012	0.785
2013	0.781
2014	0.756
2015	0.760
2016	0.764
2017	0.773
2018	0.764
2019	0.758
2020	0.750
2021	0.749
2022	0.756
2023	0.734
2024	0.716
2025	0.703
2026	0.694
2027	0.686
2028	0.678
2029	0.668