Year	Percent
1998-01-01	81.875
1999-01-01	81.950
2000-01-01	81.775
2001-01-01	81.800
2002-01-01	81.500
2003-01-01	81.000
2004-01-01	80.900
2005-01-01	81.600
2006-01-01	81.250
2007-01-01	80.300
2008-01-01	79.575
2009-01-01	79.875
2010-01-01	79.775
2011-01-01	80.425
2012-01-01	80.900
2013-01-01	81.950
2014-01-01	81.550
2015-01-01	81.425
2016-01-01	82.050
2017-01-01	82.125