Year	Percent change (Units)
1980	15.071
1981	20.680
1982	21.127
1983	20.155
1984	9.677
1985	5.882
1986	11.111
1987	3.750
1988	3.614
1989	4.651
1990	11.111
1991	7.587
1992	13.429
1993	5.828
1994	3.344
1995	8.410
1996	6.010
1997	8.574
1998	4.399
1999	4.344
2000	-2.403
2001	3.674
2002	1.918
2003	1.188
2004	-1.891
2005	0.434
2006	4.842
2007	4.400
2008	6.774
2009	1.005
2010	2.074
2011	4.473
2012	2.543
2013	1.506
2014	-0.238
2015	0.143
2016	-1.436
2017	0.783
2018	1.275
2019	1.106
2020	0.605
2021	1.863
2022	7.930
2023	3.148
2024	2.000
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000