Year	Percent
1998-01-01	75.575
1999-01-01	76.675
2000-01-01	77.175
2001-01-01	77.575
2002-01-01	77.050
2003-01-01	76.800
2004-01-01	76.475
2005-01-01	76.600
2006-01-01	77.125
2007-01-01	77.225
2008-01-01	77.950
2009-01-01	76.400
2010-01-01	76.425
2011-01-01	77.200
2012-01-01	77.075
2013-01-01	76.825
2014-01-01	76.825
2015-01-01	77.175
2016-01-01	77.725
2017-01-01	78.525