Year	Percent change (Units)
1981	0.795
1982	4.059
1983	-6.067
1984	10.265
1985	1.151
1986	0.414
1987	-1.339
1988	3.445
1989	-0.202
1990	1.112
1991	2.100
1992	2.510
1993	2.888
1994	54.008
1995	3.124
1996	6.914
1997	2.435
1998	6.404
1999	-3.259
2000	8.936
2001	2.240
2002	1.782
2003	1.184
2004	2.931
2005	3.114
2006	6.374
2007	0.332
2008	7.523
2009	-0.188
2010	4.179
2011	1.994
2012	6.890
2013	-1.785
2014	-0.737
2015	2.261
2016	-2.761
2017	2.957
2018	-0.133
2019	0.274
2020	1.159
2021	4.967
2022	2.888
2023	0.362
2024	3.000
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000