Year	Percent
1998-01-01	58.725
1999-01-01	57.375
2000-01-01	56.900
2001-01-01	56.925
2002-01-01	57.025
2003-01-01	56.350
2004-01-01	56.000
2005-01-01	56.250
2006-01-01	56.775
2007-01-01	57.275
2008-01-01	57.575
2009-01-01	56.675
2010-01-01	56.250
2011-01-01	57.250
2012-01-01	58.250
2013-01-01	59.625
2014-01-01	60.675
2015-01-01	62.375
2016-01-01	64.400
2017-01-01	66.175