Year	Ratio
1970-01-01	0.65003
1971-01-01	0.65767
1972-01-01	0.64072
1973-01-01	0.63118
1974-01-01	0.62774
1975-01-01	0.60694
1976-01-01	0.60416
1977-01-01	0.59399
1978-01-01	0.58527
1979-01-01	0.58283
1980-01-01	0.59238
1981-01-01	0.61570
1982-01-01	0.63955
1983-01-01	0.64517
1984-01-01	0.64959
1985-01-01	0.65032
1986-01-01	0.65438
1987-01-01	0.65712
1988-01-01	0.66116
1989-01-01	0.66476
1990-01-01	0.67567
1991-01-01	0.66961
1992-01-01	0.67072
1993-01-01	0.66779
1994-01-01	0.65225
1995-01-01	0.69059
1996-01-01	0.69117
1997-01-01	0.68819
1998-01-01	0.68547
1999-01-01	0.68548
2000-01-01	0.68749
2001-01-01	0.68663
2002-01-01	0.69018
2003-01-01	0.69558
2004-01-01	0.68768
2005-01-01	0.70231
2006-01-01	0.70354
2007-01-01	0.71540
2008-01-01	0.72720
2009-01-01	0.73850
2010-01-01	0.76289
2011-01-01	0.78591
2012-01-01	0.80241
2013-01-01	0.81828
2014-01-01	0.82431
2015-01-01	0.83352
2016-01-01	0.83457