Year	Ratio
1970-01-01	0.54607
1971-01-01	0.53210
1972-01-01	0.51915
1973-01-01	0.51165
1974-01-01	0.51991
1975-01-01	0.52948
1976-01-01	0.54452
1977-01-01	0.55274
1978-01-01	0.56198
1979-01-01	0.56623
1980-01-01	0.58188
1981-01-01	0.58410
1982-01-01	0.59315
1983-01-01	0.59339
1984-01-01	0.60054
1985-01-01	0.59125
1986-01-01	0.61684
1987-01-01	0.65997
1988-01-01	0.64726
1989-01-01	0.64030
1990-01-01	0.65581
1991-01-01	0.65102
1992-01-01	0.65153
1993-01-01	0.67944
1994-01-01	0.68338
1995-01-01	0.69694
1996-01-01	0.71079
1997-01-01	0.72328
1998-01-01	0.72643
1999-01-01	0.74522
2000-01-01	0.76327
2001-01-01	0.78209
2002-01-01	0.79228
2003-01-01	0.78960
2004-01-01	0.78314
2005-01-01	0.77925
2006-01-01	0.79274
2007-01-01	0.77829
2008-01-01	0.77203
2009-01-01	0.75864
2010-01-01	0.76841
2011-01-01	0.79245
2012-01-01	0.79176
2013-01-01	0.78736
2014-01-01	0.78406
2015-01-01	0.79971
2016-01-01	0.80818