Year	Ratio
1970-01-01	0.97576
1971-01-01	0.97665
1972-01-01	0.98724
1973-01-01	0.98717
1974-01-01	0.98932
1975-01-01	0.98377
1976-01-01	0.98141
1977-01-01	0.98225
1978-01-01	0.98351
1979-01-01	0.98466
1980-01-01	0.98520
1981-01-01	0.98475
1982-01-01	0.98048
1983-01-01	0.98211
1984-01-01	0.98202
1985-01-01	0.98684
1986-01-01	0.98152
1987-01-01	0.98406
1988-01-01	0.98587
1989-01-01	0.98594
1990-01-01	0.98445
1991-01-01	0.97991
1992-01-01	0.97956
1993-01-01	0.97504
1994-01-01	0.97111
1995-01-01	0.96716
1996-01-01	0.96628
1997-01-01	0.96298
1998-01-01	0.95995
1999-01-01	0.96209
2000-01-01	0.96114
2001-01-01	0.96285
2002-01-01	0.96018
2003-01-01	0.96407
2004-01-01	0.96506
2005-01-01	0.96654
2006-01-01	0.96996
2007-01-01	0.97025
2008-01-01	0.97366
2009-01-01	0.97401
2010-01-01	0.97340
2011-01-01	0.97145
2012-01-01	0.97642
2013-01-01	0.97706
2014-01-01	0.97777
2015-01-01	0.98210
2016-01-01	0.97824