Year	Percent
1998-01-01	55.950
1999-01-01	56.300
2000-01-01	55.975
2001-01-01	55.600
2002-01-01	55.500
2003-01-01	55.425
2004-01-01	55.150
2005-01-01	55.575
2006-01-01	55.500
2007-01-01	54.825
2008-01-01	54.400
2009-01-01	54.575
2010-01-01	54.325
2011-01-01	54.650
2012-01-01	55.250
2013-01-01	56.325
2014-01-01	56.300
2015-01-01	56.825
2016-01-01	57.625
2017-01-01	58.175