Year	Percent
1998-01-01	73.175
1999-01-01	73.775
2000-01-01	74.300
2001-01-01	75.075
2002-01-01	75.750
2003-01-01	76.275
2004-01-01	77.650
2005-01-01	77.425
2006-01-01	77.825
2007-01-01	77.525
2008-01-01	78.100
2009-01-01	77.200
2010-01-01	76.850
2011-01-01	76.825
2012-01-01	77.825
2013-01-01	77.125
2014-01-01	76.950
2015-01-01	76.750
2016-01-01	77.475
2017-01-01	77.850