Year	Percent
1960	0.65771
1961	0.33221
1962	0.39805
1963	0.74761
1964	0.94648
1965	0.90814
1966	0.67546
1967	0.55665
1968	0.39339
1969	0.28317
1970	0.09861
1971	0.18225
1972	0.39159
1973	0.31466
1974	0.31463
1975	0.28898
1976	0.17867
1977	0.12348
1978	0.0933
1979	0.08988
1980	0.11021
1981	-0.00264
1982	-0.02718
1983	-0.00794
1984	-0.0015
1985	0.02979
1986	0.03565
1987	0.08525
1988	0.31793
1989	0.36325
1990	0.29824
1991	0.37159
1992	0.40571
1993	0.39064
1994	0.3082
1995	0.20944
1996	0.19539
1997	0.24199
1998	0.21353
1999	0.22919
2000	0.24252
2001	0.34395
2002	0.44827
2003	0.41864
2004	0.43279
2005	0.55006
2006	0.65956
2007	0.73433
2008	0.78998
2009	0.8046
2010	0.91364
2011	1.38685
2012	0.72603
2013	0.48918
2014	0.23437
2015	0.57945
2016	0.5063
2017	0.35806