Year	Percent
1991-01-01	54.2826170460525
1992-01-01	54.1831020988286
1993-01-01	53.4161658527494
1994-01-01	53.0639228168898
1995-01-01	52.5600882223294
1996-01-01	52.6271134091812
1997-01-01	52.3153417336835
1998-01-01	51.9844003310484
1999-01-01	52.9889957197989
2000-01-01	53.1345190576545
2001-01-01	52.8369334506760
2002-01-01	52.4289901344632
2003-01-01	52.7383793358761
2004-01-01	52.5192777352803
2005-01-01	52.9649840181393
2006-01-01	53.9586715262736
2007-01-01	54.3628172140136
2008-01-01	54.8572954701388
2009-01-01	54.8691350248007
2010-01-01	55.3325872277627
2011-01-01	55.6974461364053
2012-01-01	56.4565334682636
2013-01-01	56.6394468277873
2014-01-01	56.9863304578749
2015-01-01	57.2691932673678
2016-01-01	57.1961976397148
2017-01-01	57.4016954819811