Year	Ratio
1970-01-01	0.65848
1971-01-01	0.66003
1972-01-01	0.67076
1973-01-01	0.67597
1974-01-01	0.68491
1975-01-01	0.68892
1976-01-01	0.69454
1977-01-01	0.70613
1978-01-01	0.72191
1979-01-01	0.72694
1980-01-01	0.73895
1981-01-01	0.74753
1982-01-01	0.77415
1983-01-01	0.77915
1984-01-01	0.78611
1985-01-01	0.77675
1986-01-01	0.78262
1987-01-01	0.79771
1988-01-01	0.78866
1989-01-01	0.79366
1990-01-01	0.79718
1991-01-01	0.80422
1992-01-01	0.80841
1993-01-01	0.81113
1994-01-01	0.81291
1995-01-01	0.79827
1996-01-01	0.79276
1997-01-01	0.79866
1998-01-01	0.80073
1999-01-01	0.82165
2000-01-01	0.83099
2001-01-01	0.83547
2002-01-01	0.83599
2003-01-01	0.84545
2004-01-01	0.84330
2005-01-01	0.86820
2006-01-01	0.88312
2007-01-01	0.88899
2008-01-01	0.89874
2009-01-01	0.91048
2010-01-01	0.91779
2011-01-01	0.92278
2012-01-01	0.92750
2013-01-01	0.93085
2014-01-01	0.93177
2015-01-01	0.94101
2016-01-01	0.94350