Year	Ratio
1971-01-01	0.819339990615845
1972-01-01	0.990689992904663
1973-01-01	0.830429971218109
1977-01-01	0.933879971504211
1978-01-01	0.918780028820038
1983-01-01	0.974359989166260
1984-01-01	0.972000002861023
1987-01-01	0.942269980907440
1988-01-01	0.954859972000122
1990-01-01	0.914680004119873
1991-01-01	0.916190028190613
1992-01-01	0.968230009078979
1996-01-01	0.969449996948242
1998-01-01	0.812940001487732
1999-01-01	0.959670007228851
2002-01-01	0.946839988231659
2003-01-01	0.954169988632202
2004-01-01	0.963590025901794
2005-01-01	0.961229979991913
2007-01-01	0.988039970397949
2008-01-01	0.974810004234314
2009-01-01	1.001690030097960
2010-01-01	0.990339994430542
2011-01-01	0.967630028724670
2012-01-01	0.966560006141663
2013-01-01	0.974399983882904
2014-01-01	0.959280014038086
2015-01-01	0.956239998340607
2016-01-01	0.952470004558563
2017-01-01	0.961740016937256