Year	Percent change (Units)
1981	0.782
1982	3.454
1983	3.471
1984	3.488
1985	3.505
1986	3.521
1987	3.537
1988	-13.013
1989	-11.643
1990	1.493
1991	7.353
1992	-2.740
1993	0.000
1994	19.437
1995	28.800
1996	5.500
1997	16.000
1998	-2.500
1999	3.800
2000	-3.100
2001	8.335
2002	-2.856
2003	6.704
2004	1.106
2005	3.053
2006	18.088
2007	-3.935
2008	11.813
2009	-1.773
2010	2.633
2011	1.784
2012	7.469
2013	2.087
2014	0.477
2015	4.094
2016	-0.036
2017	1.785
2018	0.897
2019	1.383
2020	0.589
2021	1.493
2022	3.212
2023	4.500
2024	3.600
2025	3.000
2026	3.000
2027	3.000
2028	3.000
2029	3.000