Year	Ratio
1971-01-01	0.901650011539459
1972-01-01	0.908739984035492
1973-01-01	0.928269982337952
1974-01-01	0.935469985008240
1975-01-01	0.941799998283386
1976-01-01	0.951680004596710
1977-01-01	0.954559981822968
1978-01-01	0.954550027847290
1979-01-01	0.961600005626678
1980-01-01	0.972230017185211
1981-01-01	0.969699978828430
1982-01-01	0.974619984626770
1983-01-01	0.976979970932007
1984-01-01	0.980229973793030
1985-01-01	0.984040021896362
1986-01-01	0.979870021343231
1987-01-01	0.997940003871918
1988-01-01	0.989139974117279
1989-01-01	0.998340010643005
1992-01-01	0.997380018234253
1994-01-01	0.996980011463165
1995-01-01	0.996320009231567
1996-01-01	1.000669956207280
1997-01-01	0.997789978981018
1999-01-01	1.003139972686770
2001-01-01	1.000210046768190
2002-01-01	0.993960022926331
2003-01-01	0.992799997329712
2011-01-01	0.970570027828217