Year	Percent change (Units)
1981	-10.600
1982	39.800
1983	-11.600
1984	4.900
1985	-1.100
1986	-21.400
1987	-21.800
1988	19.600
1989	13.100
1990	-6.000
1991	0.540
1992	21.402
1993	-32.085
1994	-4.787
1995	-0.929
1996	-7.850
1997	29.650
1998	-47.357
1999	35.976
2000	19.536
2001	6.505
2002	-21.232
2003	-18.597
2004	51.741
2005	-8.698
2006	16.936
2007	6.925
2008	12.740
2009	-12.014
2010	3.898
2011	5.895
2012	-2.707
2013	-9.569
2014	15.020
2015	13.412
2016	8.748
2017	3.483
2018	1.582
2019	17.728
2020	-3.072
2021	-7.766
2022	-3.568
2023	0.604
2024	2.588
2025	8.091
2026	3.051
2027	5.199
2028	3.186
2029	4.173