Year	Percent change (Units)
1980	6.025
1981	-18.163
1982	20.715
1983	6.583
1984	14.715
1985	17.675
1986	2.634
1987	7.919
1988	-8.543
1989	-27.798
1990	23.770
1991	-22.286
1992	-4.427
1993	-12.711
1994	1.068
1995	8.442
1996	11.420
1997	-0.597
1998	53.976
1999	29.687
2000	23.952
2001	-24.153
2002	3.044
2003	-2.625
2004	6.156
2005	11.203
2006	23.378
2007	12.473
2008	12.385
2009	-23.726
2010	-3.947
2011	12.580
2012	16.183
2013	-1.753
2014	-13.821
2015	-34.686
2016	-3.194
2017	16.843
2018	11.968
2019	8.698
2020	-35.744
2021	38.960
2022	19.865
2023	1.351
2024	3.754
2025	1.100
2026	1.691
2027	1.685
2028	1.538
2029	1.781