Year	Percent change (Units)
1980	22.499
1981	0.875
1982	-4.706
1983	13.885
1984	-21.835
1985	-35.191
1986	-3.881
1987	-3.662
1988	3.321
1989	0.181
1990	1.576
1991	2.263
1992	2.487
1993	2.771
1994	0.855
1995	6.441
1996	-7.967
1997	5.772
1998	-0.666
1999	-9.491
2000	-2.619
2001	19.977
2002	-10.006
2003	2.303
2004	18.283
2005	-6.228
2006	-6.370
2007	17.802
2008	21.767
2009	4.805
2010	0.711
2011	0.869
2012	9.410
2013	2.958
2014	-1.598
2015	-2.795
2016	5.648
2017	-0.310
2018	-1.824
2019	-2.611
2020	-41.540
2021	8.638
2022	28.480