Year	Percent change (Units)
1980	16.475
1981	-2.592
1982	-3.237
1983	-19.213
1984	-10.404
1985	-1.672
1986	2.492
1987	-3.209
1988	-3.342
1989	19.965
1990	9.298
1991	0.460
1992	-4.000
1993	27.209
1994	23.286
1995	32.924
1996	6.965
1997	22.220
1998	3.806
1999	-15.942
2000	14.735
2001	3.027
2002	-11.773
2003	-2.674
2004	13.783
2005	9.310
2006	14.823
2007	23.092
2008	14.845
2009	-11.875
2010	37.167
2011	7.313
2012	0.513
2013	7.518
2014	0.058
2015	-12.793
2016	-8.721
2017	7.790
2018	7.332
2019	4.531
2020	-8.173
2021	17.367
2022	0.389
2023	-3.278
2024	0.116
2025	1.740
2026	2.692
2027	2.401
2028	2.475
2029	2.555