Year	Ratio
1971-01-01	0.427329987287521
1972-01-01	0.423390001058578
1973-01-01	0.435999989509583
1974-01-01	0.453280001878738
1975-01-01	0.503080010414124
1976-01-01	0.525330007076263
1977-01-01	0.579129993915558
1978-01-01	0.629170000553131
1979-01-01	0.798460006713867
1980-01-01	0.864910006523132
1981-01-01	0.911660015583038
1982-01-01	0.935949981212616
1983-01-01	0.915419995784760
1984-01-01	0.887939989566803
1985-01-01	0.859250009059906
1986-01-01	0.855470001697540
1987-01-01	0.850049972534180
1988-01-01	0.867820024490356
1989-01-01	0.834819972515106
1991-01-01	0.847130000591278
1992-01-01	0.861240029335022
1993-01-01	0.854780018329620
1996-01-01	0.859600007534027
1999-01-01	0.829519987106323
2000-01-01	0.830179989337921
2003-01-01	0.847019970417023
2004-01-01	0.841610014438629
2007-01-01	0.844049990177155