Year	Percent
1998-01-01	79.325
1999-01-01	79.150
2000-01-01	79.250
2001-01-01	79.625
2002-01-01	80.050
2003-01-01	79.525
2004-01-01	78.900
2005-01-01	78.850
2006-01-01	79.200
2007-01-01	79.225
2008-01-01	79.250
2009-01-01	78.200
2010-01-01	77.875
2011-01-01	77.950
2012-01-01	77.275
2013-01-01	76.500
2014-01-01	76.700
2015-01-01	76.650
2016-01-01	77.175
2017-01-01	77.925