Year	Percent
1999-01-01	56.575
2000-01-01	57.275
2001-01-01	57.075
2002-01-01	57.075
2003-01-01	57.625
2004-01-01	57.550
2005-01-01	57.400
2006-01-01	58.050
2007-01-01	57.800
2008-01-01	56.925
2009-01-01	55.100
2010-01-01	54.225
2011-01-01	55.050
2012-01-01	55.725
2013-01-01	57.375
2014-01-01	60.775
2015-01-01	62.725
2016-01-01	65.050
2017-01-01	66.900