Year	Percent change (Units)
1980	-0.825
1981	3.079
1982	5.556
1983	3.049
1984	4.769
1985	2.956
1986	3.769
1987	2.686
1988	7.854
1989	5.992
1990	6.429
1991	7.550
1992	6.058
1993	3.982
1994	5.202
1995	4.067
1996	4.767
1997	3.269
1998	1.333
1999	1.438
2000	3.953
2001	3.296
2002	2.419
2003	4.245
2004	2.069
2005	3.326
2006	4.201
2007	4.201
2008	3.760
2009	0.362
2010	5.100
2011	5.061
2012	5.146
2013	1.772
2014	2.068
2015	3.248
2016	1.877
2017	-2.734
2018	-1.510
2019	-3.058
2020	-5.303
2021	1.700
2022	1.600
2023	1.877
2024	2.378
2025	2.520
2026	2.423
2027	2.115
2028	2.105
2029	2.084