Year	Percent
1971	-19.16661
1972	-17.90991
1973	-14.71638
1974	-12.00812
1975	-22.1058
1976	-23.25447
1977	-16.42838
1978	-16.01702
1979	-10.61569
1980	-11.25581
1981	-7.18489
1982	2.33295
1983	0.08335
1984	-1.99555
1985	2.12675
1986	6.69035
1987	5.59524
1988	7.93495
1989	8.21023
1990	11.71026
1991	16.7829
1992	16.35527
1993	9.22149
1994	12.84535
1995	11.71164
1996	8.56513
1997	5.31139
1998	15.67011
1999	16.60137
2000	18.51307
2001	25.64934
2002	25.39348
2003	28.63336
2004	20.14708
2005	21.01901
2006	20.03812
2007	16.47042
2008	20.31764
2009	20.91141
2010	21.19011
2011	20.13459
2012	12.14939
2013	16.94309
2014	19.50456
2015	25.36069
2016	27.16822