Year	Ratio
1970-01-01	0.60717
1971-01-01	0.60623
1972-01-01	0.61447
1973-01-01	0.62371
1974-01-01	0.63013
1975-01-01	0.64315
1976-01-01	0.65645
1977-01-01	0.67115
1978-01-01	0.68500
1979-01-01	0.71301
1980-01-01	0.72759
1981-01-01	0.74129
1982-01-01	0.75087
1983-01-01	0.76056
1984-01-01	0.77402
1985-01-01	0.78668
1986-01-01	0.79945
1987-01-01	0.80832
1988-01-01	0.81112
1989-01-01	0.82673
1990-01-01	0.83794
1991-01-01	0.84290
1992-01-01	0.85495
1993-01-01	0.86100
1994-01-01	0.86225
1995-01-01	0.87018
1996-01-01	0.84225
1997-01-01	0.86958
1998-01-01	0.87565
1999-01-01	0.88313
2000-01-01	0.89065
2001-01-01	0.89937
2002-01-01	0.90629
2003-01-01	0.91143
2004-01-01	0.91509
2005-01-01	0.91591
2006-01-01	0.91818
2007-01-01	0.92482
2008-01-01	0.92973
2009-01-01	0.93240
2010-01-01	0.93341
2011-01-01	0.92797
2012-01-01	0.93855
2013-01-01	0.94947
2014-01-01	0.95689
2015-01-01	0.95944
2016-01-01	0.96029