Year	Percent
1998-01-01	83.900
1999-01-01	84.150
2000-01-01	84.825
2001-01-01	85.250
2002-01-01	85.325
2003-01-01	85.900
2004-01-01	86.325
2005-01-01	87.000
2006-01-01	87.675
2007-01-01	87.700
2008-01-01	87.975
2009-01-01	87.800
2010-01-01	88.700
2011-01-01	88.375
2012-01-01	88.475
2013-01-01	88.275
2014-01-01	88.600
2015-01-01	88.775
2016-01-01	89.150
2017-01-01	89.575