Year	Percent change (Units)
1980	-14.005
1981	1.875
1982	1.516
1983	23.980
1984	-4.129
1985	-20.193
1986	-32.585
1987	-8.154
1988	-46.841
1989	71.867
1990	6.500
1991	-55.700
1992	37.600
1993	39.000
1994	-12.892
1995	34.424
1996	22.586
1997	16.227
1998	4.075
1999	36.066
2000	149.670
2001	8.115
2002	11.521
2003	13.285
2004	14.569
2005	-7.798
2006	-0.861
2007	40.613
2008	-3.913
2009	4.196
2010	5.889
2011	-33.650
2012	-65.034
2013	47.784
2014	-8.225
2015	-0.785
2016	-1.483
2017	11.884
2018	-17.556
2019	1.494
2020	-13.821
2021	20.862
2022	-3.723
2023	-70.792
2024	84.642
2025	56.524
2026	21.412
2027	13.002
2028	4.829
2029	3.831