Year	Percent
1960	13.96932
1961	7.15845
1962	2.13378
1963	5.69006
1964	7.75616
1965	13.34661
1966	-0.54645
1967	-10.67416
1968	3.50877
1969	10.75697
1970	9.48814
1971	12.90984
1972	8.42199
1973	14.22078
1974	22.27171
1975	16.04128
1976	8.10127
1977	-3.25265
1978	-23.73396
1979	-36.32171
1980	-39.44469
1981	-30.64484
1982	-35.25784
1983	-38.30613
1984	-37.24469
1985	-36.17072
1986	-11.00068
1987	-0.26066
1988	-3.40049
1989	-2.77929
1990	-9.85928
1991	-11.37732
1992	-18.74371
1993	-19.09128
1994	-9.18643
1995	-13.73164
1996	-21.27756
1997	-14.80103
1998	-17.60294
1999	-16.26674
2000	-13.72472
2001	-11.39605
2002	-9.1808
2003	-1.51841
2004	-6.92867
2005	-11.9062
2006	-10.3934
2007	-10.53794
2008	-13.91788
2009	-14.62986
2010	-13.10703
2011	-12.70645
2012	-9.98003
2013	-6.17418
2014	-4.89653
2015	-0.47714
2016	-3.16271