Year	Percent
1999-01-01	77.900
2000-01-01	78.825
2001-01-01	78.425
2002-01-01	79.250
2003-01-01	80.025
2004-01-01	80.300
2005-01-01	80.925
2006-01-01	81.250
2007-01-01	81.350
2008-01-01	81.575
2009-01-01	80.825
2010-01-01	80.650
2011-01-01	80.400
2012-01-01	80.075
2013-01-01	79.775
2014-01-01	79.550
2015-01-01	79.525
2016-01-01	79.175
2017-01-01	78.925