Year	Percent change (Units)
1980	30.941
1981	-2.512
1982	-6.529
1983	15.849
1984	-20.531
1985	-33.623
1986	-2.766
1987	-8.813
1988	5.547
1989	0.536
1990	1.080
1991	1.549
1992	1.701
1993	2.041
1994	1.347
1995	6.445
1996	-6.722
1997	57.134
1998	2.332
1999	-1.676
2000	-4.770
2001	15.485
2002	-19.032
2003	28.188
2004	16.518
2005	-8.326
2006	-2.465
2007	11.885
2008	20.859
2009	9.371
2010	-10.250
2011	-3.554
2012	4.319
2013	7.304
2014	0.494
2015	5.057
2016	3.329
2017	0.337
2018	-1.433
2019	-4.645
2020	-50.684
2021	2.442
2022	25.585