Year	Percent change (Units)
1981	-25.900
1982	38.500
1983	-10.600
1984	11.300
1985	2.400
1986	-17.400
1987	-18.300
1988	12.700
1989	13.100
1990	-12.700
1991	0.540
1992	21.402
1993	-32.085
1994	-4.787
1995	-0.929
1996	-7.850
1997	29.650
1998	-46.025
1999	33.519
2000	19.064
2001	7.019
2002	-20.189
2003	-18.282
2004	50.278
2005	-9.135
2006	16.633
2007	9.440
2008	12.583
2009	-11.009
2010	4.443
2011	5.051
2012	-5.255
2013	-8.789
2014	16.718
2015	13.810
2016	10.185
2017	10.366
2018	7.636
2019	13.576
2020	-5.711
2021	-5.841
2022	-4.518
2023	0.556
2024	3.036
2025	7.766
2026	3.455
2027	5.115
2028	3.407
2029	4.330