Year	Percent change (Units)
1980	8.420
1981	5.977
1982	24.992
1983	-8.840
1984	14.934
1985	5.159
1986	17.780
1987	20.329
1988	23.541
1989	22.914
1990	12.627
1991	17.215
1992	10.927
1993	11.485
1994	17.715
1995	13.376
1996	0.634
1997	12.242
1998	-0.848
1999	12.057
2000	24.235
2001	0.497
2002	3.959
2003	11.682
2004	14.420
2005	7.481
2006	11.176
2007	11.756
2008	4.832
2009	-13.738
2010	16.690
2011	8.724
2012	2.228
2013	0.370
2014	0.946
2015	-1.845
2016	0.402
2017	5.638
2018	3.925
2019	-3.667
2020	-5.814
2021	15.472
2022	1.201
2023	-2.882
2024	2.600
2025	3.500
2026	3.500
2027	3.934
2028	3.849
2029	3.529