Year	Ratio
1971-01-01	0.403829991817474
1972-01-01	0.426490008831024
1974-01-01	0.488020002841949
1975-01-01	0.496329993009567
1976-01-01	0.541490018367767
1977-01-01	0.560970008373261
1978-01-01	0.589219987392426
1979-01-01	0.612110018730164
1980-01-01	0.625329971313477
1981-01-01	0.632189989089966
1982-01-01	0.652469992637634
1983-01-01	0.673089981079102
1984-01-01	0.683409988880157
1985-01-01	0.680119991302490
1986-01-01	0.667670011520386
1987-01-01	0.670539975166321
1988-01-01	0.662649989128113
1989-01-01	0.662810027599335
1990-01-01	0.716080009937286
1991-01-01	0.728259980678558
1992-01-01	0.719850003719330
1993-01-01	0.729569971561432
1994-01-01	0.732689976692200
1995-01-01	0.744409978389740
1996-01-01	0.747080028057098
1997-01-01	0.756129980087280
1998-01-01	0.772549986839294
1999-01-01	0.787769973278046
2000-01-01	0.798789978027344
2001-01-01	0.806010007858276
2002-01-01	0.811200022697449
2003-01-01	0.826359987258911
2004-01-01	0.837289988994598
2005-01-01	0.852900028228760
2006-01-01	0.866360008716583
2007-01-01	0.871940016746521
2008-01-01	0.868009984493256
2009-01-01	0.866410017013550
2010-01-01	0.870880007743835
2011-01-01	0.862720012664795
2012-01-01	0.854229986667633