Year	Ratio
1970-01-01	0.66216
1971-01-01	0.65393
1972-01-01	0.62838
1973-01-01	0.61440
1974-01-01	0.60018
1975-01-01	0.58361
1976-01-01	0.56637
1977-01-01	0.57085
1978-01-01	0.55070
1979-01-01	0.54068
1980-01-01	0.54584
1981-01-01	0.54485
1982-01-01	0.54919
1983-01-01	0.54815
1984-01-01	0.54983
1985-01-01	0.55813
1986-01-01	0.54920
1987-01-01	0.55548
1988-01-01	0.55460
1989-01-01	0.55500
1990-01-01	0.55929
1991-01-01	0.55219
1992-01-01	0.55579
1993-01-01	0.55611
1994-01-01	0.56245
1995-01-01	0.56791
1996-01-01	0.57689
1997-01-01	0.58788
1998-01-01	0.60545
1999-01-01	0.61917
2000-01-01	0.63066
2001-01-01	0.62829
2002-01-01	0.65285
2003-01-01	0.63966
2004-01-01	0.64637
2005-01-01	0.64884
2006-01-01	0.66404
2007-01-01	0.65911
2008-01-01	0.64345
2009-01-01	0.64710
2010-01-01	0.64329
2011-01-01	0.64290
2012-01-01	0.66595
2013-01-01	0.66307
2014-01-01	0.65481
2015-01-01	0.66584
2016-01-01	0.67129