Year	Percent change (Units)
1981	1.630
1982	3.699
1983	12.023
1984	7.978
1985	3.205
1986	2.929
1987	3.701
1988	2.978
1989	2.604
1990	-0.047
1991	-2.291
1992	1.311
1993	9.763
1994	16.687
1995	15.627
1996	4.422
1997	13.337
1998	8.180
1999	6.211
2000	13.292
2001	-1.124
2002	-0.015
2003	5.210
2004	11.394
2005	5.876
2006	9.282
2007	4.572
2008	0.902
2009	-19.192
2010	14.876
2011	8.570
2012	-0.519
2013	-3.370
2014	3.474
2015	1.917
2016	2.593
2017	5.706
2018	5.120
2019	4.508
2020	-3.478
2021	9.471
2022	3.680
2023	1.492
2024	3.200
2025	3.200
2026	3.200
2027	3.200
2028	3.200
2029	3.200