Year	Ratio
1970-01-01	0.80349
1971-01-01	0.80176
1972-01-01	0.79906
1973-01-01	0.79569
1974-01-01	0.79263
1975-01-01	0.85152
1976-01-01	0.88255
1977-01-01	0.88978
1978-01-01	0.88842
1979-01-01	0.88395
1980-01-01	0.88625
1981-01-01	0.88384
1982-01-01	0.87533
1983-01-01	0.87177
1984-01-01	0.87694
1985-01-01	0.88040
1986-01-01	0.90311
1987-01-01	0.90894
1988-01-01	0.91643
1989-01-01	0.92247
1990-01-01	0.93069
1991-01-01	0.93593
1992-01-01	0.94365
1993-01-01	0.94598
1994-01-01	0.95022
1995-01-01	0.95677
1996-01-01	0.96162
1997-01-01	0.96561
1998-01-01	0.96939
1999-01-01	0.97328
2000-01-01	0.97464
2001-01-01	0.97934
2002-01-01	0.97838
2003-01-01	0.97996
2004-01-01	0.98405
2005-01-01	0.98276
2006-01-01	0.98086
2007-01-01	0.97949
2008-01-01	0.97658
2009-01-01	0.97806
2010-01-01	0.97579
2011-01-01	0.97718
2012-01-01	0.98257
2013-01-01	0.98696
2014-01-01	0.99188
2015-01-01	0.99069
2016-01-01	0.99075