Year	Ratio
1970-01-01	0.97547
1971-01-01	0.97808
1972-01-01	0.98973
1973-01-01	0.99505
1974-01-01	0.99746
1975-01-01	0.98800
1976-01-01	0.97815
1977-01-01	0.98037
1978-01-01	0.98048
1979-01-01	0.98221
1980-01-01	0.98126
1981-01-01	0.97879
1982-01-01	0.97481
1983-01-01	0.97603
1984-01-01	0.97587
1985-01-01	0.98287
1986-01-01	0.97693
1987-01-01	0.98510
1988-01-01	0.98572
1989-01-01	0.98514
1990-01-01	0.98051
1991-01-01	0.97635
1992-01-01	0.97894
1993-01-01	0.97480
1994-01-01	0.96740
1995-01-01	0.96140
1996-01-01	0.95958
1997-01-01	0.95506
1998-01-01	0.95096
1999-01-01	0.95341
2000-01-01	0.95340
2001-01-01	0.95551
2002-01-01	0.95062
2003-01-01	0.95630
2004-01-01	0.95835
2005-01-01	0.96049
2006-01-01	0.96493
2007-01-01	0.96500
2008-01-01	0.96926
2009-01-01	0.97037
2010-01-01	0.96945
2011-01-01	0.96571
2012-01-01	0.97077
2013-01-01	0.97394
2014-01-01	0.97499
2015-01-01	0.97527
2016-01-01	0.97549