Year	Ratio
1971-01-01	0.580799996852875
1972-01-01	0.583369970321655
1973-01-01	0.587599992752075
1974-01-01	0.586099982261658
1975-01-01	0.613070011138916
1976-01-01	0.643869996070862
1977-01-01	0.661979973316193
1978-01-01	0.677929997444153
1982-01-01	0.709010004997253
1983-01-01	0.732599973678589
1984-01-01	0.769190013408661
1985-01-01	0.791419982910156
1986-01-01	0.810450017452240
1987-01-01	0.818289995193481
1988-01-01	0.838519990444183
1989-01-01	0.860199987888336
1990-01-01	0.881600022315979
1991-01-01	0.900349974632263
1992-01-01	0.914939999580383
1993-01-01	0.927160024642944
1994-01-01	0.934769988059998
1995-01-01	0.933279991149902
1996-01-01	0.928409993648529
1997-01-01	0.929889976978302
1998-01-01	0.928799986839294
1999-01-01	0.937609970569611
2000-01-01	0.943620026111603
2001-01-01	0.947780013084412
2002-01-01	0.954349994659424
2003-01-01	0.961600005626678
2004-01-01	0.967329978942871
2005-01-01	0.975440025329590
2006-01-01	0.975030004978180
2007-01-01	0.986720025539398
2008-01-01	0.993849992752075
2009-01-01	0.993040025234222
2010-01-01	0.990869998931885
2011-01-01	0.981790006160736
2012-01-01	0.981069982051849
2013-01-01	1.017820000648500
2014-01-01	1.048660039901730
2015-01-01	1.054610013961790