Year	Percent change (Units)
1980	8.937
1981	1.328
1982	-13.463
1983	0.017
1984	-8.885
1985	-14.651
1986	0.101
1987	16.663
1988	15.847
1989	-10.725
1990	-26.733
1991	22.030
1992	3.926
1993	-10.363
1994	15.737
1995	-15.497
1996	21.612
1997	13.664
1998	-17.661
1999	-4.026
2000	-9.577
2001	-9.712
2002	-4.020
2003	1.250
2004	9.018
2005	-8.955
2006	20.549
2007	22.493
2008	-0.903
2009	20.188
2010	-3.902
2011	5.183
2012	13.127
2013	16.333
2014	-22.856
2015	-13.174
2016	-12.381
2017	32.483
2018	11.088
2019	5.848
2020	-3.349
2021	10.712
2022	3.683
2023	9.195
2024	-2.659
2025	7.949
2026	6.260
2027	4.863
2028	4.772
2029	4.977