Year	Ratio
1971-01-01	0.580399990081787
1972-01-01	0.608500003814697
1973-01-01	0.635060012340546
1974-01-01	0.654190003871918
1975-01-01	0.660380005836487
1976-01-01	0.673030018806458
1977-01-01	0.688069999217987
1978-01-01	0.702269971370697
1979-01-01	0.718640029430389
1980-01-01	0.756470024585724
1981-01-01	0.776530027389526
1982-01-01	0.802770018577576
1983-01-01	0.820280015468597
1984-01-01	0.841989994049072
1985-01-01	0.861069977283478
1986-01-01	0.879050016403198
1987-01-01	0.895449995994568
1988-01-01	0.899420022964478
1989-01-01	0.901880025863647
1990-01-01	0.903970003128052
1991-01-01	0.905260026454926
1992-01-01	0.905939996242523
1993-01-01	0.911539971828461
1994-01-01	0.912710011005402
1995-01-01	0.913309991359711
1996-01-01	0.912429988384247
1997-01-01	0.914900004863739
1998-01-01	0.925530016422272
1999-01-01	0.918569982051849
2000-01-01	0.925130009651184
2001-01-01	0.934660017490387
2002-01-01	0.940190017223358
2003-01-01	0.956610023975372
2004-01-01	0.962629973888397
2005-01-01	0.971449971199036
2006-01-01	0.972940027713776
2007-01-01	0.972800016403198
2008-01-01	0.972519993782043
2009-01-01	0.969340026378632
2010-01-01	0.964980006217957
2011-01-01	0.967100024223328
2012-01-01	0.963680028915405
2013-01-01	0.966419994831085