Year	Percent change (Units)
1980	35.974
1981	-5.617
1982	28.120
1983	-7.150
1984	12.394
1985	-7.328
1986	-4.838
1987	-6.977
1988	-5.312
1989	-2.186
1990	36.780
1991	-26.360
1992	-62.153
1993	74.917
1994	-21.955
1995	31.812
1996	9.645
1997	25.753
1998	52.541
1999	14.637
2000	-2.621
2001	-4.486
2002	-8.302
2003	17.987
2004	6.489
2005	16.544
2006	5.483
2007	2.340
2008	-11.509
2009	14.311
2010	0.263
2011	30.589
2012	-1.588
2013	21.668
2014	5.540
2015	9.824
2016	3.740
2017	-1.678
2018	6.623
2019	10.891
2020	-23.916
2021	19.795
2022	3.050
2023	-23.724
2024	-11.770
2025	11.053
2026	2.039
2027	2.120
2028	2.122
2029	2.122