Year	Ratio
1970-01-01	0.97082
1971-01-01	0.96934
1972-01-01	0.96175
1973-01-01	0.96726
1974-01-01	0.97095
1975-01-01	0.96539
1976-01-01	0.96483
1977-01-01	0.97142
1978-01-01	0.96998
1979-01-01	0.97257
1980-01-01	0.97756
1981-01-01	0.97652
1982-01-01	0.97605
1983-01-01	0.97413
1984-01-01	0.97469
1985-01-01	0.97940
1986-01-01	0.98120
1987-01-01	0.98157
1988-01-01	0.98688
1989-01-01	0.98601
1990-01-01	0.98890
1991-01-01	0.98131
1992-01-01	0.98205
1993-01-01	0.97855
1994-01-01	0.97432
1995-01-01	0.97342
1996-01-01	0.97179
1997-01-01	0.97103
1998-01-01	0.96939
1999-01-01	0.97692
2000-01-01	0.97246
2001-01-01	0.97166
2002-01-01	0.97049
2003-01-01	0.97363
2004-01-01	0.97377
2005-01-01	0.97023
2006-01-01	0.97251
2007-01-01	0.97396
2008-01-01	0.96951
2009-01-01	0.97562
2010-01-01	0.97031
2011-01-01	0.97105
2012-01-01	0.98339
2013-01-01	0.97898
2014-01-01	0.98182
2015-01-01	0.98471
2016-01-01	0.98236