Year	Percent
1999-01-01	81.725
2000-01-01	79.650
2001-01-01	78.975
2002-01-01	79.475
2003-01-01	80.475
2004-01-01	79.975
2005-01-01	81.350
2006-01-01	84.125
2007-01-01	85.050
2008-01-01	86.450
2009-01-01	84.200
2010-01-01	81.400
2011-01-01	82.500
2012-01-01	83.000
2013-01-01	82.225
2014-01-01	83.200
2015-01-01	85.100
2016-01-01	86.350
2017-01-01	86.325