Year	Percent change (Units)
1980	13.477
1981	11.960
1982	11.869
1983	7.162
1984	5.941
1985	5.607
1986	8.850
1987	7.317
1988	5.682
1989	4.301
1990	4.296
1991	2.801
1992	2.244
1993	1.881
1994	1.846
1995	2.115
1996	1.775
1997	2.326
1998	2.415
1999	2.774
2000	2.969
2001	2.097
2002	2.696
2003	0.625
2004	1.118
2005	1.843
2006	2.171
2007	2.834
2008	2.181
2009	2.022
2010	2.753
2011	0.107
2012	1.392
2013	2.006
2014	2.070
2015	2.333
2016	3.469
2017	1.628
2018	3.487
2019	1.366
2020	1.438
2021	5.314
2022	5.887
2023	4.766
2024	3.300
2025	2.600
2026	2.000
2027	2.000
2028	2.000
2029	2.000