Year	Ratio
1971-01-01	0.279529988765717
1972-01-01	0.301719993352890
1973-01-01	0.300669997930527
1974-01-01	0.313109993934631
1981-01-01	0.436520010232925
1983-01-01	0.420340001583099
1984-01-01	0.432749986648560
1999-01-01	0.539950013160706
2014-01-01	0.704649984836578
2015-01-01	0.714739978313446
2016-01-01	0.727980017662048