Year	Ratio
1971-01-01	0.353960007429123
1972-01-01	0.368459999561310
1973-01-01	0.384810000658035
1974-01-01	0.401329994201660
1975-01-01	0.411139994859695
1976-01-01	0.427769988775253
1977-01-01	0.431600004434586
1978-01-01	0.439269989728928
1984-01-01	0.463640004396439
1985-01-01	0.465119987726212
1988-01-01	0.501699984073639
1989-01-01	0.495799988508224
1990-01-01	0.516569972038269
1991-01-01	0.566449999809265
2001-01-01	0.705649971961975
2011-01-01	0.732079982757568
2012-01-01	0.838850021362305
2013-01-01	0.853929996490479
2015-01-01	0.862510025501251
2016-01-01	0.909479975700378