Year	Ratio
1970-01-01	0.97084
1971-01-01	0.97165
1972-01-01	0.97094
1973-01-01	0.97390
1974-01-01	0.97171
1975-01-01	0.97930
1976-01-01	0.98131
1977-01-01	0.98175
1978-01-01	0.98263
1979-01-01	0.98340
1980-01-01	0.98524
1981-01-01	0.99277
1982-01-01	0.98912
1983-01-01	0.99389
1984-01-01	0.99284
1985-01-01	0.99304
1986-01-01	0.99441
1987-01-01	0.99478
1988-01-01	0.99372
1989-01-01	0.99003
1990-01-01	0.98984
1991-01-01	0.99198
1992-01-01	0.99432
1993-01-01	0.99036
1994-01-01	0.98812
1995-01-01	0.98830
1996-01-01	0.99104
1997-01-01	0.99064
1998-01-01	0.98822
1999-01-01	0.98551
2000-01-01	0.98614
2001-01-01	0.98234
2002-01-01	0.97961
2003-01-01	0.97699
2004-01-01	0.98011
2005-01-01	0.98095
2006-01-01	0.98278
2007-01-01	0.98348
2008-01-01	0.98584
2009-01-01	0.98647
2010-01-01	0.98392
2011-01-01	0.98222
2012-01-01	0.98509
2013-01-01	0.99318
2014-01-01	0.99348
2015-01-01	0.99317
2016-01-01	0.99450