Year	Percent
1998-01-01	84.325
1999-01-01	84.175
2000-01-01	83.950
2001-01-01	83.075
2002-01-01	81.875
2003-01-01	80.725
2004-01-01	79.450
2005-01-01	78.500
2006-01-01	77.525
2007-01-01	76.550
2008-01-01	75.400
2009-01-01	74.025
2010-01-01	73.100
2011-01-01	71.175
2012-01-01	67.825
2013-01-01	65.350
2014-01-01	61.725
2015-01-01	60.400
2016-01-01	58.275
2017-01-01	55.475