Year	Ratio
1970-01-01	0.602479994297028
1971-01-01	0.597999989986420
1972-01-01	0.579069972038269
1973-01-01	0.572049975395203
1974-01-01	0.587059974670410
1975-01-01	0.626550018787384
1976-01-01	0.628069996833801
1977-01-01	0.655139982700348
1978-01-01	0.688740015029907
1979-01-01	0.722199976444244
1981-01-01	0.762499988079071
1982-01-01	0.789489984512329
1984-01-01	0.813319981098175
1986-01-01	0.828220009803772
1987-01-01	0.837369978427887
1988-01-01	0.839559972286224
1989-01-01	0.838479995727539
1990-01-01	0.842299997806549
1991-01-01	0.850049972534180
1992-01-01	0.850239992141724
1993-01-01	0.865429997444153
1994-01-01	0.862360000610352
1995-01-01	0.874459981918335
1996-01-01	0.857209980487823
1997-01-01	0.869830012321472
1998-01-01	0.870949983596802
2000-01-01	0.862240016460419
2001-01-01	0.857649981975555
2002-01-01	0.846599996089935
2003-01-01	0.855499982833862
2004-01-01	0.863799989223480
2005-01-01	0.846570014953613
2006-01-01	0.846229970455170
2008-01-01	0.885349988937378
2012-01-01	0.904410004615784