Year	Ratio
1970-01-01	0.922720015048981
1971-01-01	0.919650018215179
1972-01-01	0.931469976902008
1973-01-01	0.928789973258972
1974-01-01	0.937170028686523
1975-01-01	0.937879979610443
1976-01-01	0.934909999370575
1977-01-01	0.936410009860992
1978-01-01	0.938669979572296
1979-01-01	0.938120007514954
1980-01-01	0.939859986305237
1981-01-01	0.940039992332459
1982-01-01	0.937340021133423
1983-01-01	0.935350000858307
1984-01-01	0.938709974288940
1985-01-01	0.943189978599548
1986-01-01	0.949060022830963
1987-01-01	0.953519999980927
1988-01-01	0.956780016422272
1989-01-01	0.963469982147217
1990-01-01	0.962570011615753
1991-01-01	0.965969979763031
1992-01-01	0.962949991226196
1993-01-01	0.966059982776642
1994-01-01	0.966120004653931
1995-01-01	0.969929993152618
1996-01-01	0.970499992370605
1997-01-01	0.971480011940002
1998-01-01	0.967890024185181
1999-01-01	0.962249994277954
2000-01-01	0.962300002574921
2001-01-01	0.963540017604828
2002-01-01	0.964089989662170
2003-01-01	0.966740012168884
2004-01-01	0.969460010528564
2005-01-01	0.971560001373291
2006-01-01	0.970539987087250
2007-01-01	0.968829989433289
2008-01-01	0.967899978160858
2009-01-01	0.968110024929047
2010-01-01	0.961340010166168
2011-01-01	0.963580012321472
2012-01-01	0.968729972839355