Year	Ratio
1970-01-01	0.65033
1971-01-01	0.64716
1972-01-01	0.65844
1973-01-01	0.66329
1974-01-01	0.67329
1975-01-01	0.68101
1976-01-01	0.68625
1977-01-01	0.69654
1978-01-01	0.70483
1979-01-01	0.72410
1980-01-01	0.74102
1981-01-01	0.75606
1982-01-01	0.78839
1983-01-01	0.79021
1984-01-01	0.79169
1985-01-01	0.77555
1986-01-01	0.78138
1987-01-01	0.80417
1988-01-01	0.79809
1989-01-01	0.79731
1990-01-01	0.79526
1991-01-01	0.80289
1992-01-01	0.80577
1993-01-01	0.80379
1994-01-01	0.80107
1995-01-01	0.78789
1996-01-01	0.78713
1997-01-01	0.78553
1998-01-01	0.78625
1999-01-01	0.80324
2000-01-01	0.80565
2001-01-01	0.80464
2002-01-01	0.80177
2003-01-01	0.81173
2004-01-01	0.79602
2005-01-01	0.82462
2006-01-01	0.83214
2007-01-01	0.83565
2008-01-01	0.84708
2009-01-01	0.85620
2010-01-01	0.86522
2011-01-01	0.87065
2012-01-01	0.87751
2013-01-01	0.88262
2014-01-01	0.88489
2015-01-01	0.90160
2016-01-01	0.90258