Year	Percent change (Units)
1980	18.329
1981	-12.079
1982	10.245
1983	26.688
1984	23.571
1985	38.905
1986	-11.828
1987	-3.892
1988	9.102
1989	-2.678
1990	12.667
1991	0.944
1992	7.462
1993	-5.017
1994	-6.394
1995	18.848
1996	-12.798
1997	11.264
1998	4.054
1999	5.010
2000	-4.017
2001	26.989
2002	-9.450
2003	15.548
2004	38.031
2005	6.512
2006	13.688
2007	1.303
2008	19.636
2009	-12.805
2010	18.871
2011	12.348
2012	4.054
2013	25.929
2014	10.726
2015	46.523
2016	15.851
2017	-20.619
2018	-12.286
2019	10.746
2020	7.839
2021	10.324
2022	-17.445
2023	20.730
2024	2.752
2025	4.932
2026	5.369
2027	4.408
2028	3.966
2029	3.455