Year	Percent change (Units)
1981	56.639
1982	-26.169
1983	43.590
1984	-17.979
1985	17.435
1986	58.585
1987	18.366
1988	14.545
1989	-25.096
1990	18.744
1991	-6.411
1992	59.306
1993	0.942
1994	23.441
1995	107.535
1996	88.837
1997	152.190
1998	39.524
1999	20.043
2000	-11.150
2001	40.072
2002	13.350
2003	3.238
2004	58.850
2005	48.769
2006	6.790
2007	3.102
2008	20.567
2009	-15.923
2010	0.186
2011	-7.722
2012	7.725
2013	-3.190
2014	6.508
2015	0.482
2016	-13.587
2017	-18.332
2018	-2.323
2019	-19.105
2020	18.729
2021	16.952
2022	-14.242
2023	-15.297
2024	7.361
2025	-15.403
2026	-14.732
2027	-4.619
2028	-8.844
2029	-4.532