Year	Percent change (Units)
1981	9.127
1982	-5.448
1983	-15.229
1984	6.027
1985	13.633
1986	2.128
1987	11.621
1988	-7.455
1989	-26.896
1990	33.915
1991	6.465
1992	-14.104
1993	10.122
1994	-4.938
1995	-11.669
1996	-2.902
1997	-1.834
1998	42.138
1999	-8.157
2000	5.215
2001	-1.346
2002	33.599
2003	-2.795
2004	21.727
2005	18.105
2006	6.985
2007	5.560
2008	9.003
2009	6.414
2010	54.547
2011	23.932
2012	9.927
2013	1.879
2014	10.018
2015	6.504
2016	11.673
2017	19.424
2018	5.963
2019	-0.052
2020	-2.710
2021	7.061
2022	-6.509
2023	-9.120
2024	7.405
2025	6.530
2026	2.332
2027	3.229
2028	5.642
2029	5.864