Year	Ratio
1971-01-01	0.655089974403381
1972-01-01	0.686479985713959
1974-01-01	0.707449972629547
1988-01-01	0.839100003242493
1989-01-01	0.927590012550354
1990-01-01	0.944090008735657
2005-01-01	0.957629978656769
2006-01-01	0.948790013790131
2007-01-01	0.950720012187958
2008-01-01	0.942470014095306
2009-01-01	0.939119994640350
2011-01-01	0.949729979038239
2012-01-01	0.953769981861115
2014-01-01	0.980729997158051
2015-01-01	0.989009976387024
2016-01-01	0.994589984416962