Year	Percent change (Units)
1980	42.820
1981	29.361
1982	20.532
1983	51.511
1984	66.125
1985	83.001
1986	70.652
1987	57.285
1988	69.007
1989	89.177
1990	128.954
1991	81.449
1992	58.911
1993	52.882
1994	44.091
1995	35.443
1996	24.328
1997	15.169
1998	8.627
1999	4.169
2000	5.083
2001	3.567
2002	25.978
2003	10.195
2004	7.569
2005	4.887
2006	6.373
2007	8.514
2008	9.202
2009	5.914
2010	6.924
2011	8.590
2012	7.478
2013	8.523
2014	8.266
2015	9.444
2016	8.090
2017	6.551
2018	7.961
2019	8.801
2020	9.401
2021	7.970
2022	8.291
2023	5.113
2024	5.700
2025	5.500
2026	5.300
2027	5.000
2028	4.700
2029	4.600