Year	Percent
1999-01-01	52.325
2000-01-01	52.600
2001-01-01	53.350
2002-01-01	54.450
2003-01-01	54.850
2004-01-01	53.125
2005-01-01	54.125
2006-01-01	55.000
2007-01-01	56.050
2008-01-01	57.125
2009-01-01	57.400
2010-01-01	57.725
2011-01-01	58.100
2012-01-01	58.425
2013-01-01	58.425
2014-01-01	58.475
2015-01-01	58.850
2016-01-01	59.500
2017-01-01	59.975