Year	Ratio
1970-01-01	0.91337
1971-01-01	0.89687
1972-01-01	0.93038
1973-01-01	0.92152
1974-01-01	0.94729
1975-01-01	0.95297
1976-01-01	0.94238
1977-01-01	0.94603
1978-01-01	0.94463
1979-01-01	0.94906
1980-01-01	0.95114
1981-01-01	0.95356
1982-01-01	0.95749
1983-01-01	0.95852
1984-01-01	0.96221
1985-01-01	0.96580
1986-01-01	0.96916
1987-01-01	0.96838
1988-01-01	0.96911
1989-01-01	0.97158
1990-01-01	0.97399
1991-01-01	0.97117
1992-01-01	0.96441
1993-01-01	0.96485
1994-01-01	0.96636
1995-01-01	0.97400
1996-01-01	0.97204
1997-01-01	0.97330
1998-01-01	0.98063
1999-01-01	0.97917
2000-01-01	0.97414
2001-01-01	0.98265
2002-01-01	0.98514
2003-01-01	0.98219
2004-01-01	0.97780
2005-01-01	0.98525
2006-01-01	0.98236
2007-01-01	0.98095
2008-01-01	0.98874
2009-01-01	0.98466
2010-01-01	0.98967
2011-01-01	0.99143
2012-01-01	0.99543
2013-01-01	0.99845
2014-01-01	0.98953
2015-01-01	0.99183
2016-01-01	0.99139