Year	Ratio
1970-01-01	0.987680017948151
1971-01-01	0.987810015678406
1972-01-01	0.990670025348663
1973-01-01	0.986039996147156
1974-01-01	0.981769979000092
1975-01-01	0.983370006084442
1976-01-01	0.978470027446747
1977-01-01	0.976750016212463
1978-01-01	0.969160020351410
1979-01-01	0.969850003719330
1980-01-01	0.967850029468536
1981-01-01	0.965149998664856
1982-01-01	0.968689978122711
1983-01-01	0.966750025749207
1984-01-01	0.966750025749207
1985-01-01	0.972310006618500
1986-01-01	0.974279999732971
1987-01-01	0.976530015468597
1988-01-01	0.980690002441406
1989-01-01	0.979430019855499
1990-01-01	0.983190000057220
1991-01-01	0.986370027065277
1992-01-01	0.985539972782135
1993-01-01	0.985920011997223
1994-01-01	0.985669970512390
1995-01-01	0.986720025539398
1996-01-01	0.989199995994568
1997-01-01	0.982569992542267
1998-01-01	0.983190000057220
1999-01-01	0.973900020122528
2000-01-01	0.968469977378845
2001-01-01	0.983060002326965
2002-01-01	0.968900024890900
2004-01-01	0.976490020751953
2005-01-01	0.974520027637482
2006-01-01	0.978699982166290
2007-01-01	0.980359971523285
2008-01-01	0.982079982757568
2009-01-01	0.980180025100708
2010-01-01	0.980589985847473
2011-01-01	0.982479989528656
2012-01-01	0.984820008277893
2013-01-01	0.987349987030029
2014-01-01	0.991209983825684
2015-01-01	0.994270026683807
2016-01-01	1.005699992179870