Year	Percent change (Units)
1980	8.635
1981	8.128
1982	6.429
1983	7.875
1984	20.300
1985	5.071
1986	-13.054
1987	-2.730
1988	14.900
1989	-4.900
1990	0.500
1991	4.200
1992	-3.800
1993	-10.874
1994	41.272
1995	5.364
1996	11.331
1997	5.572
1998	4.259
1999	-8.447
2000	3.823
2001	12.431
2002	5.192
2003	-1.753
2004	-4.803
2005	4.449
2006	9.640
2007	-7.440
2008	8.333
2009	10.103
2010	-2.110
2011	2.029
2012	7.517
2013	0.223
2014	1.682
2015	4.833
2016	-1.613
2017	-0.912
2018	4.027
2019	-0.971
2020	5.320
2021	-1.624
2022	6.885
2023	2.682
2024	3.087
2025	3.087
2026	3.087
2027	3.087
2028	3.087
2029	3.087