Year	Ratio
1971-01-01	0.178100004792213
1972-01-01	0.162169992923737
1973-01-01	0.216030001640320
1976-01-01	0.251630008220673
1977-01-01	0.215320006012917
1978-01-01	0.229389995336533
1979-01-01	0.288989990949631
1980-01-01	0.282779991626740
1983-01-01	0.339289993047714
1984-01-01	0.365689992904663
1987-01-01	0.395799994468689
1988-01-01	0.418300002813339
1989-01-01	0.437970012426376
1990-01-01	0.426440000534058
1999-01-01	0.561680018901825
2001-01-01	0.680970013141632
2003-01-01	0.586769998073578