Year	Percent
1981	0.15552
1982	0.24956
1983	0.36026
1984	0.26163
1985	0.36347
1986	0.32269
1987	0.50705
1988	0.68327
1989	0.72206
1990	1.02976
1991	1.27077
1992	1.38799
1993	1.2683
1994	1.19225
1995	2.15008
1996	2.7242
1997	2.1678
1998	-0.25229
1999	-1.33257
2000	-2.75744
2001	-1.85569
2002	0.07415
2003	-0.25426
2004	0.73824
2005	2.91611
2006	1.34794
2007	1.60301
2008	1.82633
2009	0.90392
2010	2.02518
2011	2.30298
2012	2.30978
2013	2.55136
2014	2.81997
2015	2.29762
2016	0.48717
2017	2.11361