Year	Ratio
1970-01-01	0.76412
1971-01-01	0.76252
1972-01-01	0.76203
1973-01-01	0.77035
1974-01-01	0.78263
1975-01-01	0.79542
1976-01-01	0.80051
1977-01-01	0.80638
1978-01-01	0.82013
1979-01-01	0.82666
1980-01-01	0.82412
1981-01-01	0.81935
1982-01-01	0.81620
1983-01-01	0.82557
1984-01-01	0.81663
1985-01-01	0.81129
1986-01-01	0.82810
1987-01-01	0.83620
1988-01-01	0.83889
1989-01-01	0.84368
1990-01-01	0.84476
1991-01-01	0.84926
1992-01-01	0.85417
1993-01-01	0.85730
1994-01-01	0.86842
1995-01-01	0.87703
1996-01-01	0.88261
1997-01-01	0.89120
1998-01-01	0.90329
1999-01-01	0.91294
2000-01-01	0.91589
2001-01-01	0.91806
2002-01-01	0.92147
2003-01-01	0.93500
2004-01-01	0.93683
2005-01-01	0.94431
2006-01-01	0.94771
2007-01-01	0.95412
2008-01-01	0.96028
2009-01-01	0.97031
2010-01-01	0.96519
2011-01-01	0.96776
2012-01-01	0.97114
2013-01-01	0.98319
2014-01-01	0.98749
2015-01-01	0.98623
2016-01-01	0.98729