Year	Percent
1999-01-01	55.550
2000-01-01	56.225
2001-01-01	56.200
2002-01-01	56.225
2003-01-01	57.025
2004-01-01	56.750
2005-01-01	56.900
2006-01-01	57.350
2007-01-01	57.025
2008-01-01	56.400
2009-01-01	55.050
2010-01-01	54.950
2011-01-01	55.425
2012-01-01	56.675
2013-01-01	58.075
2014-01-01	61.775
2015-01-01	63.950
2016-01-01	66.525
2017-01-01	68.175