Year	Percent change (Units)
1980	30.783
1981	-2.903
1982	-5.299
1983	-13.622
1984	2.569
1985	2.437
1986	-25.786
1987	-12.183
1988	1.096
1989	0.357
1990	15.590
1991	-4.950
1992	0.005
1993	-11.028
1994	12.448
1995	23.071
1996	-3.350
1997	13.420
1998	9.326
1999	11.545
2000	23.146
2001	6.438
2002	-4.432
2003	17.599
2004	11.307
2005	28.069
2006	30.010
2007	-13.406
2008	19.445
2009	-41.043
2010	5.163
2011	36.217
2012	-2.592
2013	9.102
2014	-8.863
2015	-8.849
2016	-20.278
2017	5.975
2018	0.925
2019	-17.081
2020	-26.777
2021	39.871
2022	30.965
2023	-27.543
2024	-5.824
2025	5.724
2026	0.141
2027	1.123
2028	2.010
2029	4.152