Year	Ratio
1971-01-01	0.438369989395142
1972-01-01	0.436859995126724
1973-01-01	0.474959999322891
1979-01-01	0.559809982776642
1980-01-01	0.572799980640411
1984-01-01	0.648670017719269
1988-01-01	0.677779972553253
2008-01-01	1.152029991149900
2012-01-01	1.309919953346250
2015-01-01	1.160269975662230