Year	Ratio
1991-01-01	0.978720009326935
1992-01-01	0.974349975585938
1993-01-01	0.959959983825684
1994-01-01	0.962880015373230
1995-01-01	0.966889977455139
1996-01-01	0.945070028305054
1997-01-01	0.972159981727600
1998-01-01	0.951879978179932
1999-01-01	0.945039987564087
2000-01-01	0.927600026130676
2001-01-01	0.927829980850220
2002-01-01	0.955460011959076
2003-01-01	0.956340014934540
2004-01-01	0.957539975643158
2005-01-01	0.967299997806549
2006-01-01	0.960940003395081
2007-01-01	0.971830010414124
2008-01-01	0.972339987754822
2009-01-01	0.974829971790314
2010-01-01	0.976520001888275
2011-01-01	0.972379982471466
2012-01-01	0.979390025138855
2013-01-01	0.979809999465942
2014-01-01	0.987789988517761
2015-01-01	0.986240029335022
2016-01-01	0.985239982604980
2017-01-01	0.985849976539612