Year	Percent
1980	-13.19641
1981	-21.95438
1982	-22.59414
1983	-15.92593
1984	-7.70507
1985	-12.81377
1986	-2.61137
1987	-2.13343
1988	-5.82725
1989	-9.39006
1990	2.1547
1991	-10.57967
1992	-3.19977
1993	-3.49361
1994	-2.6063
1995	-1.15
1996	-0.26246
1997	-2.92787
1998	-4.34623
1999	-12.29725
2000	-20.70132
2001	-18.23113
2002	-13.57029
2003	-12.75116
2004	-7.95283
2005	-8.0346
2006	-0.51793
2007	-0.12377
2008	-7.28171
2009	-4.5992
2010	0.74053
2011	-3.00965
2012	-0.46931
2013	-5.50707
2014	-5.50199
2015	-9.07634
2016	-10.81242
2017	-8.81393