Year	Ratio
1970-01-01	0.43986
1971-01-01	0.43121
1972-01-01	0.42095
1973-01-01	0.41699
1974-01-01	0.38817
1975-01-01	0.40284
1976-01-01	0.42119
1977-01-01	0.43545
1978-01-01	0.45006
1979-01-01	0.41921
1980-01-01	0.42708
1981-01-01	0.43395
1982-01-01	0.46575
1983-01-01	0.42885
1984-01-01	0.41744
1985-01-01	0.42595
1986-01-01	0.41654
1987-01-01	0.45038
1988-01-01	0.43237
1989-01-01	0.43153
1990-01-01	0.42363
1991-01-01	0.42531
1992-01-01	0.43417
1993-01-01	0.46877
1994-01-01	0.48272
1995-01-01	0.50099
1996-01-01	0.52025
1997-01-01	0.54008
1998-01-01	0.55631
1999-01-01	0.58502
2000-01-01	0.60596
2001-01-01	0.61705
2002-01-01	0.60264
2003-01-01	0.59014
2004-01-01	0.59198
2005-01-01	0.60726
2006-01-01	0.61385
2007-01-01	0.60378
2008-01-01	0.60309
2009-01-01	0.61548
2010-01-01	0.63046
2011-01-01	0.64267
2012-01-01	0.66636
2013-01-01	0.68185
2014-01-01	0.68398
2015-01-01	0.68987
2016-01-01	0.68876