Year	Percent
1998-01-01	75.075
1999-01-01	75.725
2000-01-01	77.400
2001-01-01	78.150
2002-01-01	78.325
2003-01-01	79.625
2004-01-01	80.550
2005-01-01	81.675
2006-01-01	82.625
2007-01-01	82.750
2008-01-01	82.875
2009-01-01	83.275
2010-01-01	84.850
2011-01-01	84.500
2012-01-01	85.050
2013-01-01	85.525
2014-01-01	85.850
2015-01-01	86.050
2016-01-01	86.575
2017-01-01	87.025