Year	Percent change (Units)
1980	-20.544
1981	32.478
1982	-16.432
1983	26.469
1984	13.496
1985	-10.982
1986	28.213
1987	-2.923
1988	-22.490
1989	-0.424
1990	23.998
1991	-6.625
1992	-3.660
1993	-9.957
1994	-60.261
1995	21.340
1996	39.357
1997	13.374
1998	-12.454
1999	13.897
2000	-3.889
2001	18.021
2002	10.082
2003	3.659
2004	28.250
2005	13.494
2006	12.501
2007	-0.147
2008	21.750
2009	-20.183
2010	11.687
2011	19.794
2012	21.238
2013	9.609
2014	8.551
2015	-3.766
2016	9.814
2017	29.582
2018	7.374
2019	-5.140
2020	-15.329
2021	34.518
2022	14.761
2023	19.292
2024	14.239
2025	8.207
2026	8.743
2027	9.401
2028	8.531
2029	5.987