Year	Percent change (Units)
1981	6.543
1982	13.423
1983	2.750
1984	7.493
1985	0.996
1986	-3.533
1987	2.981
1988	2.151
1989	1.619
1990	-1.355
1991	-0.889
1992	-0.163
1993	2.696
1994	29.091
1995	3.941
1996	6.931
1997	4.178
1998	0.972
1999	0.659
2000	2.409
2001	0.976
2002	3.935
2003	3.165
2004	0.692
2005	4.472
2006	1.528
2007	2.267
2008	11.578
2009	-1.844
2010	-0.261
2011	5.060
2012	1.674
2013	0.120
2014	-0.149
2015	2.867
2016	-0.302
2017	1.640
2018	0.336
2019	-2.556
2020	2.318
2021	8.198
2022	9.328
2023	1.055
2024	2.600
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000