Year	Percent
1960	1.45819
1961	1.30934
1962	1.35207
1963	1.57967
1964	1.8873
1965	1.50721
1966	1.62441
1967	1.60917
1968	1.54267
1969	1.49926
1970	1.38013
1971	1.24611
1972	1.20229
1973	1.18499
1974	1.27688
1975	1.45128
1976	1.3652
1977	1.34595
1978	1.42921
1979	1.43385
1980	1.42025
1981	1.38005
1982	1.413
1983	1.39118
1984	1.41416
1985	1.51262
1986	1.50876
1987	1.41668
1988	1.29918
1989	1.23415
1990	1.19566
1991	1.15422
1992	1.09921
1993	1.11558
1994	1.09445
1995	1.07323
1996	1.04968
1997	1.04643
1998	1.01807
1999	0.98025
2000	0.98032
2001	0.90824
2002	0.88353
2003	0.91364
2004	0.89348
2005	0.85372
2006	0.78978
2007	0.90566
2008	0.87617
2009	0.83878
2010	0.82477
2011	0.79474
2012	0.78223
2013	0.75402
2014	0.75395
2015	0.7071
2016	0.747
2017	0.72936