Year	Ratio
1970-01-01	0.723959982395172
1971-01-01	0.847329974174500
1972-01-01	0.858650028705597
1973-01-01	0.847280025482178
1974-01-01	0.871540009975433
1975-01-01	0.884400010108948
1976-01-01	0.885370016098022
1977-01-01	0.908819973468781
1978-01-01	0.807009994983673
1979-01-01	0.818970024585724
1980-01-01	0.830470025539398
1981-01-01	0.858669996261597
1982-01-01	0.860920011997223
1983-01-01	0.883819997310638
1993-01-01	0.886290013790131
1996-01-01	0.888639986515045
1998-01-01	0.895789980888367
1999-01-01	0.843580007553101
2000-01-01	0.892199993133545
2001-01-01	0.901430010795593
2002-01-01	0.898479998111725
2004-01-01	0.914189994335175
2005-01-01	0.922829985618591
2006-01-01	0.933499991893768
2007-01-01	0.941860020160675
2008-01-01	0.954490005970001
2009-01-01	0.955519974231720
2010-01-01	0.942789971828461
2011-01-01	0.935360014438629
2012-01-01	0.940050005912781
2013-01-01	0.939310014247894
2014-01-01	0.949079990386963
2015-01-01	0.943170011043549
2016-01-01	0.947640001773834