Year	Percent
1998-01-01	77.100
1999-01-01	77.900
2000-01-01	78.125
2001-01-01	77.875
2002-01-01	78.775
2003-01-01	79.800
2004-01-01	81.150
2005-01-01	81.475
2006-01-01	81.950
2007-01-01	81.825
2008-01-01	81.950
2009-01-01	82.750
2010-01-01	83.250
2011-01-01	83.125
2012-01-01	83.750
2013-01-01	83.875
2014-01-01	84.350
2015-01-01	85.375
2016-01-01	85.475
2017-01-01	85.000