Year Ratio 1970-01-01 0.0540100000798702 1971-01-01 0.2437199950218200 1972-01-01 0.2198199927806850 1974-01-01 0.3153800070285800 1976-01-01 0.3740600049495700 1977-01-01 0.3899500072002410 1978-01-01 0.3912799954414370 1979-01-01 0.4189800024032590 1982-01-01 0.4706000089645390 1983-01-01 0.4883500039577480 1984-01-01 0.5042399764060970 1985-01-01 0.5322499871253970 1986-01-01 0.5482100248336790 1988-01-01 0.6046800017356870 1991-01-01 0.5985100269317630 1992-01-01 0.7471200227737430 1993-01-01 0.7591099739074710 1994-01-01 0.7748699784278870 1995-01-01 0.7837200164794920 1996-01-01 0.7995799779891970 1997-01-01 0.8189899921417240 1998-01-01 0.8358100056648250 1999-01-01 0.8551099896430970 2000-01-01 0.8767600059509280 2001-01-01 0.8941799998283390 2002-01-01 0.9114199876785280 2003-01-01 0.9422399997711180 2004-01-01 0.9718999862670900 2005-01-01 0.9770500063896180 2006-01-01 0.9884099960327150 2007-01-01 0.9929100275039670 2008-01-01 1.0124499797821000 2009-01-01 1.0208100080490100 2010-01-01 1.0255000591278100 2011-01-01 1.0176199674606300 2012-01-01 1.0187499523162800 2013-01-01 1.0136300325393700 2014-01-01 1.0171099901199300 2015-01-01 1.0119199752807600 2016-01-01 1.0067499876022300