Year	Ratio
1970-01-01	0.67714
1971-01-01	0.67738
1972-01-01	0.65711
1973-01-01	0.64234
1974-01-01	0.63028
1975-01-01	0.62038
1976-01-01	0.61194
1977-01-01	0.60038
1978-01-01	0.58353
1979-01-01	0.56676
1980-01-01	0.56034
1981-01-01	0.54821
1982-01-01	0.54363
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	0.52630
1989-01-01	0.52281
1990-01-01	0.51908
1991-01-01	0.53592
1992-01-01	0.55452
1993-01-01	0.56962
1994-01-01	0.60415
1995-01-01	0.62203
1996-01-01	0.64019
1997-01-01	0.65591
1998-01-01	0.67919
1999-01-01	0.70064
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	0.70590
2008-01-01	0.69893
2009-01-01	0.70582
2010-01-01	0.70320
2011-01-01	0.68792
2012-01-01	0.71249
2013-01-01	0.72163
2014-01-01	0.71734
2015-01-01	0.72817
2016-01-01	0.72943