Year	Ratio
1970-01-01	0.64841
1971-01-01	0.64665
1972-01-01	0.65218
1973-01-01	0.65937
1974-01-01	0.66602
1975-01-01	0.67332
1976-01-01	0.68016
1977-01-01	0.69037
1978-01-01	0.70126
1979-01-01	0.72700
1980-01-01	0.74126
1981-01-01	0.75389
1982-01-01	0.76330
1983-01-01	0.76851
1984-01-01	0.77450
1985-01-01	0.78341
1986-01-01	0.79258
1987-01-01	0.80074
1988-01-01	0.79934
1989-01-01	0.81096
1990-01-01	0.81702
1991-01-01	0.81766
1992-01-01	0.82813
1993-01-01	0.83394
1994-01-01	0.83598
1995-01-01	0.84628
1996-01-01	0.81929
1997-01-01	0.84957
1998-01-01	0.85727
1999-01-01	0.86520
2000-01-01	0.87370
2001-01-01	0.88406
2002-01-01	0.89040
2003-01-01	0.89661
2004-01-01	0.90106
2005-01-01	0.90531
2006-01-01	0.90656
2007-01-01	0.90853
2008-01-01	0.91447
2009-01-01	0.91896
2010-01-01	0.92237
2011-01-01	0.91769
2012-01-01	0.92895
2013-01-01	0.93030
2014-01-01	0.93428
2015-01-01	0.93934
2016-01-01	0.93795