Year	Percent change (Units)
1980	27.877
1981	11.100
1982	-0.810
1983	9.891
1984	0.991
1985	-9.158
1986	9.100
1987	11.700
1988	6.484
1989	7.164
1990	15.542
1991	12.500
1992	16.857
1993	20.126
1994	3.386
1995	5.488
1996	6.244
1997	7.579
1998	-1.410
1999	2.956
2000	-1.178
2001	0.673
2002	0.927
2003	-2.803
2004	6.339
2005	2.460
2006	3.500
2007	6.795
2008	12.041
2009	4.530
2010	6.150
2011	11.273
2012	10.891
2013	3.997
2014	2.448
2015	1.371
2016	0.801
2017	2.272
2018	1.367
2019	1.326
2020	-1.594
2021	0.213
2022	2.601
2023	2.616
2024	3.777
2025	3.000
2026	2.037
2027	2.000
2028	2.000
2029	2.000