Year	Percent (Units)
1980	1.415
1981	1.491
1982	1.518
1983	1.545
1984	1.591
1985	1.596
1986	1.654
1987	1.698
1988	1.738
1989	1.829
1990	1.916
1991	2.037
1992	1.954
1993	2.069
1994	2.161
1995	2.255
1996	2.341
1997	2.356
1998	1.991
1999	1.939
2000	1.943
2001	1.966
2002	1.998
2003	2.012
2004	2.007
2005	2.026
2006	2.031
2007	2.052
2008	2.142
2009	2.252
2010	2.276
2011	2.326
2012	2.391
2013	2.394
2014	2.386
2015	2.360
2016	2.356
2017	2.359
2018	2.395
2019	2.448
2020	2.469
2021	2.406
2022	2.452
2023	2.498
2024	2.542
2025	2.588
2026	2.636
2027	2.686
2028	2.738
2029	2.792