Year	Ratio
1970-01-01	0.68533
1971-01-01	0.68347
1972-01-01	0.68087
1973-01-01	0.68577
1974-01-01	0.68541
1975-01-01	0.67557
1976-01-01	0.66826
1977-01-01	0.66165
1978-01-01	0.66094
1979-01-01	0.65102
1980-01-01	0.64204
1981-01-01	0.64619
1982-01-01	0.65250
1983-01-01	0.61456
1984-01-01	0.59273
1985-01-01	0.64901
1986-01-01	0.71143
1987-01-01	0.73300
1988-01-01	0.73776
1989-01-01	0.74565
1990-01-01	0.75833
1991-01-01	0.76812
1992-01-01	0.77804
1993-01-01	0.78363
1994-01-01	0.78540
1995-01-01	0.80408
1996-01-01	0.81125
1997-01-01	0.81541
1998-01-01	0.81557
1999-01-01	0.81718
2000-01-01	0.80242
2001-01-01	0.79699
2002-01-01	0.77726
2003-01-01	0.78375
2004-01-01	0.78083
2005-01-01	0.78734
2006-01-01	0.78581
2007-01-01	0.77732
2008-01-01	0.79624
2009-01-01	0.80886
2010-01-01	0.82041
2011-01-01	0.82674
2012-01-01	0.84695
2013-01-01	0.86147
2014-01-01	0.86634
2015-01-01	0.86524
2016-01-01	0.86680