Year	Percent change (Units)
1980	13.641
1981	4.300
1982	5.000
1983	4.300
1984	-1.800
1985	-3.200
1986	-4.100
1987	-3.390
1988	-7.814
1989	3.074
1990	15.120
1991	-4.109
1992	11.783
1993	-11.310
1994	6.895
1995	3.294
1996	20.075
1997	6.437
1998	0.471
1999	13.624
2000	-4.574
2001	-3.838
2002	1.587
2003	-3.586
2004	18.245
2005	4.416
2006	1.151
2007	-11.148
2008	-4.608
2009	11.054
2010	-7.723
2011	2.175
2012	7.125
2013	3.567
2014	12.552
2015	-2.681
2016	-7.381
2017	13.513
2018	-2.252
2019	16.670
2020	-2.355
2021	10.205
2022	7.765
2023	3.343
2024	-3.676
2025	10.356
2026	9.046
2027	7.686
2028	6.677
2029	5.921