Year	Ratio
1970-01-01	0.67713
1971-01-01	0.67737
1972-01-01	0.65710
1973-01-01	0.64232
1974-01-01	0.63027
1975-01-01	0.62036
1976-01-01	0.61193
1977-01-01	0.60037
1978-01-01	0.58352
1979-01-01	0.56675
1980-01-01	0.56033
1981-01-01	0.54820
1982-01-01	0.54362
1983-01-01	0.54312
1984-01-01	0.54286
1985-01-01	0.53503
1986-01-01	0.53334
1987-01-01	0.54593
1988-01-01	0.52629
1989-01-01	0.52281
1990-01-01	0.51907
1991-01-01	0.53592
1992-01-01	0.55451
1993-01-01	0.56962
1994-01-01	0.60415
1995-01-01	0.62203
1996-01-01	0.64018
1997-01-01	0.65590
1998-01-01	0.67918
1999-01-01	0.70063
2000-01-01	0.70124
2001-01-01	0.69398
2002-01-01	0.69845
2003-01-01	0.68328
2004-01-01	0.69323
2005-01-01	0.69553
2006-01-01	0.70597
2007-01-01	0.70589
2008-01-01	0.69892
2009-01-01	0.70581
2010-01-01	0.70319
2011-01-01	0.68788
2012-01-01	0.71247
2013-01-01	0.72160
2014-01-01	0.71729
2015-01-01	0.72807
2016-01-01	0.72932