Year	Percent
1998-01-01	70.775
1999-01-01	72.050
2000-01-01	73.900
2001-01-01	74.650
2002-01-01	74.000
2003-01-01	74.250
2004-01-01	74.850
2005-01-01	74.775
2006-01-01	75.225
2007-01-01	74.825
2008-01-01	75.800
2009-01-01	74.900
2010-01-01	74.575
2011-01-01	74.100
2012-01-01	72.500
2013-01-01	72.200
2014-01-01	74.325
2015-01-01	76.075
2016-01-01	77.575
2017-01-01	79.675