Year	Percent (Units)
1980	1.685
1981	1.556
1982	1.909
1983	2.071
1984	1.841
1985	1.811
1986	1.579
1987	1.519
1988	1.365
1989	1.397
1990	1.526
1991	1.678
1992	1.561
1993	1.508
1994	1.440
1995	1.422
1996	1.457
1997	1.419
1998	1.409
1999	1.389
2000	1.403
2001	1.402
2002	1.474
2003	1.539
2004	1.525
2005	1.503
2006	1.500
2007	1.541
2008	1.501
2009	1.522
2010	1.530
2011	1.512
2012	1.284
2013	1.181
2014	1.143
2015	1.008
2016	1.048
2017	1.044
2018	0.990
2019	0.934
2020	0.993
2021	0.978
2022	0.982
2023	0.997
2024	0.999
2025	0.997
2026	0.994
2027	0.986
2028	0.976
2029	0.966