Year	Percent
1960	2.31068
1961	1.79337
1962	1.2739
1963	1.37145
1964	1.46481
1965	1.52632
1966	1.61184
1967	1.69291
1968	1.63851
1969	1.53469
1970	1.2824
1971	1.66797
1972	1.88685
1973	1.77945
1974	1.77208
1975	1.90437
1976	2.02865
1977	2.05541
1978	2.07972
1979	1.86556
1980	1.57786
1981	0.88459
1982	0.31404
1983	0.14621
1984	0.12516
1985	0.10418
1986	0.18725
1987	0.20764
1988	0.2486
1989	0.28926
1990	0.39123
1991	0.61463
1992	0.83393
1993	0.90736
1994	0.95886
1995	1.02849
1996	0.41237
1997	-0.21579
1998	-0.23594
1999	-0.35496
2000	-0.51495
2001	0.03971
2002	0.65289
2003	0.51141
2004	0.41116
2005	0.37055
2006	0.31098
2007	0.27132
2008	0.25128
2009	0.25065
2010	0.26923
2011	0.36423
2012	0.45819
2013	0.5698
2014	0.64187
2015	0.67517
2016	0.68921
2017	0.77663