Year	Percent
1998-01-01	83.975
1999-01-01	84.325
2000-01-01	84.875
2001-01-01	85.475
2002-01-01	85.975
2003-01-01	86.500
2004-01-01	86.825
2005-01-01	86.650
2006-01-01	87.200
2007-01-01	87.350
2008-01-01	86.750
2009-01-01	84.725
2010-01-01	83.600
2011-01-01	83.425
2012-01-01	81.725
2013-01-01	79.175
2014-01-01	78.225
2015-01-01	78.600
2016-01-01	79.350
2017-01-01	79.825