Year	Ratio
1971-01-01	0.394760012626648
1972-01-01	0.414640009403229
1973-01-01	0.434850007295609
1974-01-01	0.458759993314743
1976-01-01	0.531899988651276
1977-01-01	0.575720012187958
1978-01-01	0.599810004234314
1979-01-01	0.606249988079071
1980-01-01	0.643230020999908
1981-01-01	0.664979994297028
1982-01-01	0.647660017013550
1983-01-01	0.661180019378662
1984-01-01	0.684090018272400
1985-01-01	0.713259994983673
1986-01-01	0.733870029449463
1987-01-01	0.726289987564087
1988-01-01	0.769450008869171
1989-01-01	0.879980027675629
1994-01-01	0.911230027675629
1995-01-01	0.839450001716614
1996-01-01	0.905290007591248
1997-01-01	0.883059978485107
1999-01-01	0.877030014991760