Year	Percent
1998-01-01	51.500
1999-01-01	51.875
2000-01-01	52.700
2001-01-01	52.825
2002-01-01	54.600
2003-01-01	56.475
2004-01-01	57.700
2005-01-01	58.600
2006-01-01	60.575
2007-01-01	60.850
2008-01-01	61.950
2009-01-01	62.300
2010-01-01	61.125
2011-01-01	57.750
2012-01-01	53.925
2013-01-01	51.350
2014-01-01	53.100
2015-01-01	55.400
2016-01-01	55.950
2017-01-01	57.250