Year	Ratio
1970-01-01	0.61506
1971-01-01	0.61364
1972-01-01	0.63455
1973-01-01	0.63103
1974-01-01	0.62816
1975-01-01	0.63666
1976-01-01	0.64410
1977-01-01	0.67142
1978-01-01	0.68546
1979-01-01	0.69221
1980-01-01	0.70394
1981-01-01	0.72753
1982-01-01	0.74878
1983-01-01	0.72755
1984-01-01	0.74863
1985-01-01	0.74044
1986-01-01	0.74533
1987-01-01	0.75431
1988-01-01	0.76875
1989-01-01	0.77617
1990-01-01	0.78673
1991-01-01	0.79899
1992-01-01	0.80398
1993-01-01	0.80906
1994-01-01	0.81477
1995-01-01	0.80675
1996-01-01	0.80706
1997-01-01	0.81374
1998-01-01	0.81882
1999-01-01	0.83878
2000-01-01	0.84763
2001-01-01	0.85459
2002-01-01	0.85882
2003-01-01	0.86765
2004-01-01	0.86729
2005-01-01	0.89035
2006-01-01	0.90449
2007-01-01	0.91067
2008-01-01	0.91779
2009-01-01	0.92559
2010-01-01	0.93293
2011-01-01	0.92799
2012-01-01	0.92987
2013-01-01	0.93088
2014-01-01	0.93368
2015-01-01	0.94315
2016-01-01	0.94129