Year	Percent change (Units)
1987	7.263
1988	9.956
1989	7.906
1990	2.623
1991	9.987
1992	-6.272
1993	0.950
1994	5.367
1995	7.792
1996	1.246
1997	12.992
1998	8.992
1999	6.956
2000	11.645
2001	6.743
2002	-3.125
2003	0.026
2004	8.102
2005	3.064
2006	4.691
2007	-1.063
2008	6.903
2009	-20.674
2010	17.809
2011	11.524
2012	-2.750
2013	0.195
2014	1.536
2015	4.910
2016	-2.385
2017	5.609
2018	-0.893
2019	1.242
2020	-9.678
2021	17.502
2022	-12.054
2023	-1.068
2024	1.300
2025	2.600
2026	2.500
2027	2.500
2028	2.500
2029	2.500