Year	Percent
1998-01-01	56.350
1999-01-01	56.500
2000-01-01	56.900
2001-01-01	57.250
2002-01-01	57.600
2003-01-01	57.975
2004-01-01	57.700
2005-01-01	57.300
2006-01-01	57.525
2007-01-01	57.475
2008-01-01	57.075
2009-01-01	55.575
2010-01-01	54.650
2011-01-01	54.300
2012-01-01	53.450
2013-01-01	51.900
2014-01-01	51.750
2015-01-01	52.225
2016-01-01	52.800
2017-01-01	53.250