Year	Ratio
1971-01-01	0.530529975891113
1972-01-01	0.555119991302490
1973-01-01	0.567740023136139
1974-01-01	0.574140012264252
1975-01-01	0.585030019283295
1976-01-01	0.590460002422333
1977-01-01	0.600359976291656
1985-01-01	0.702459990978241
1988-01-01	0.684409976005554
1990-01-01	0.710160017013550
1991-01-01	0.742240011692047
1992-01-01	0.750909984111786
1993-01-01	0.775279998779297
1994-01-01	0.798200011253357
1995-01-01	0.832300007343292
1997-01-01	0.899590015411377
1999-01-01	0.924700021743774
2000-01-01	0.936010003089905
2001-01-01	0.940710008144379
2002-01-01	0.942870020866394
2003-01-01	0.938260018825531
2004-01-01	0.959599971771240
2005-01-01	0.963320016860962
2006-01-01	0.970439970493317
2007-01-01	1.010660052299500
2008-01-01	0.981069982051849
2009-01-01	0.976819992065430
2010-01-01	0.980669975280762
2011-01-01	0.985400021076202
2012-01-01	0.981989979743958
2013-01-01	0.988829970359802
2014-01-01	0.993680000305176
2015-01-01	1.002300024032590