Year	Percent
1991-01-01	57.2081746816920
1992-01-01	57.2592631566531
1993-01-01	57.2652055691661
1994-01-01	57.4140807677857
1995-01-01	57.0476412488461
1996-01-01	56.8105883889412
1997-01-01	56.5191122822226
1998-01-01	56.3672643033430
1999-01-01	56.1586997416400
2000-01-01	55.7973301664945
2001-01-01	55.9536252266685
2002-01-01	56.1214680639781
2003-01-01	56.3864779785241
2004-01-01	56.6627724969797
2005-01-01	56.9812344844646
2006-01-01	56.4190877532158
2007-01-01	55.6901607406172
2008-01-01	54.8349307460199
2009-01-01	54.2099105415101
2010-01-01	53.6524599233161
2011-01-01	53.1237442293559
2012-01-01	52.5437629493491
2013-01-01	52.5701279337944
2014-01-01	52.6272393544625
2015-01-01	52.5870117559357
2016-01-01	52.6740520699579
2017-01-01	52.5680318922289