Year	Percent
1999-01-01	72.725
2000-01-01	73.775
2001-01-01	74.475
2002-01-01	76.225
2003-01-01	76.875
2004-01-01	74.725
2005-01-01	75.250
2006-01-01	75.950
2007-01-01	76.725
2008-01-01	77.825
2009-01-01	78.375
2010-01-01	78.925
2011-01-01	79.850
2012-01-01	80.400
2013-01-01	80.475
2014-01-01	80.300
2015-01-01	80.250
2016-01-01	80.575
2017-01-01	81.025