Year	Percent change (Units)
1980	4.612
1981	5.361
1982	-0.817
1983	4.615
1984	-1.566
1985	-4.084
1986	-1.015
1987	-0.706
1988	-12.400
1989	-1.694
1990	-0.132
1991	-0.154
1992	0.400
1993	-0.400
1994	5.000
1995	5.912
1996	6.344
1997	3.967
1998	3.712
1999	7.036
2000	4.102
2001	2.961
2002	0.754
2003	2.521
2004	5.351
2005	4.244
2006	3.805
2007	5.076
2008	3.436
2009	-3.293
2010	4.410
2011	6.317
2012	6.496
2013	4.927
2014	4.785
2015	4.792
2016	4.563
2017	4.631
2018	-3.363
2019	-2.897
2020	-1.766
2021	10.347
2022	3.751
2023	4.686
2024	3.500
2025	3.500
2026	3.500
2027	3.500
2028	3.500
2029	3.500