Year	Percent change (Units)
1980	-50.260
1981	46.636
1982	11.570
1983	-15.462
1984	18.571
1985	14.600
1986	-12.629
1987	8.917
1988	1.766
1989	-10.015
1990	0.413
1991	15.859
1992	16.672
1993	-21.015
1994	-24.561
1995	33.897
1996	-51.809
1997	87.117
1998	-26.088
1999	7.448
2000	4.724
2001	4.000
2002	-18.692
2003	29.491
2004	-11.377
2005	2.817
2006	-19.662
2007	15.410
2008	-11.431
2009	0.728
2010	13.600
2011	3.310
2012	14.582
2013	-7.051
2014	34.751
2015	-2.843
2016	19.527
2017	31.509
2018	15.477
2019	-4.677
2020	-21.629
2021	-6.428
2022	15.034
2023	3.569
2024	32.807
2025	9.525
2026	23.658
2027	16.877
2028	7.012
2029	11.247