Year	Ratio
1971-01-01	0.422969996929169
1972-01-01	0.647870004177094
1973-01-01	0.768209993839264
1976-01-01	0.534919977188110
1978-01-01	0.477739989757538
1979-01-01	0.456189990043640
1980-01-01	0.455370008945465
1981-01-01	0.462080001831055
1982-01-01	0.463710010051727
1983-01-01	0.486059993505478
1984-01-01	0.503639996051788
1985-01-01	0.514289975166321
1987-01-01	0.542639970779419
1988-01-01	0.539789974689484
1989-01-01	0.553610026836395
1992-01-01	0.548680007457733
1993-01-01	0.552730023860931
1994-01-01	0.563080012798309
1995-01-01	0.576789975166321
1996-01-01	0.576359987258911
1997-01-01	0.575760006904602
1998-01-01	0.576409995555878
2000-01-01	0.670819997787476
2010-01-01	0.933960020542145