Year	Percent
1960	0.5108
1961	0.54847
1962	0.6129
1963	0.64236
1964	0.66655
1965	0.64973
1966	0.7014
1967	0.74743
1968	0.51925
1969	0.34533
1970	0.34922
1971	0.44625
1972	0.58119
1973	0.55404
1974	0.17021
1975	-0.26532
1976	-0.17667
1977	0.03839
1978	-0.08096
1979	-0.17046
1980	0.00011
1981	0.25502
1982	0.07172
1983	-0.1616
1984	-0.00629
1985	0.04695
1986	0.06355
1987	0.06328
1988	0.14157
1989	0.45051
1990	0.762
1991	0.99842
1992	1.10055
1993	0.82463
1994	0.38487
1995	0.15311
1996	0.13502
1997	0.11332
1998	0.10973
1999	0.19456
2000	0.24047
2001	0.3828
2002	0.49198
2003	0.48713
2004	0.62041
2005	0.68127
2006	0.4948
2007	0.32415
2008	0.31304
2009	0.26195
2010	0.24039
2011	0.33708
2012	0.45594
2013	0.58939
2014	0.78154
2015	1.12099
2016	1.0814
2017	0.82691