Year	Percent change (Units)
1980	-6.560
1981	-13.624
1982	-10.002
1983	-20.025
1984	1.255
1985	-3.558
1986	36.714
1987	-6.269
1988	-10.925
1989	14.932
1990	8.155
1991	9.505
1992	-2.209
1993	29.571
1994	29.070
1995	38.812
1996	6.111
1997	16.880
1998	2.558
1999	-14.193
2000	13.111
2001	2.668
2002	-11.801
2003	-3.545
2004	16.990
2005	5.204
2006	16.027
2007	23.664
2008	17.424
2009	-17.463
2010	37.121
2011	8.597
2012	-1.726
2013	7.632
2014	-2.380
2015	-15.276
2016	-11.087
2017	10.205
2018	14.518
2019	5.697
2020	-3.458
2021	22.738
2022	-2.286
2023	-6.513
2024	-0.726
2025	1.243
2026	2.237
2027	1.787
2028	1.880
2029	1.939