Year	Percent
1998-01-01	75.625
1999-01-01	77.125
2000-01-01	77.350
2001-01-01	78.150
2002-01-01	79.225
2003-01-01	78.850
2004-01-01	78.150
2005-01-01	78.950
2006-01-01	79.625
2007-01-01	80.650
2008-01-01	81.225
2009-01-01	80.500
2010-01-01	79.175
2011-01-01	79.575
2012-01-01	79.400
2013-01-01	78.075
2014-01-01	78.125
2015-01-01	77.300
2016-01-01	76.650
2017-01-01	77.850