Year	Percent
1998-01-01	63.975
1999-01-01	64.125
2000-01-01	63.600
2001-01-01	63.175
2002-01-01	62.725
2003-01-01	62.550
2004-01-01	62.200
2005-01-01	62.400
2006-01-01	62.325
2007-01-01	61.475
2008-01-01	61.050
2009-01-01	61.475
2010-01-01	61.525
2011-01-01	62.200
2012-01-01	63.500
2013-01-01	65.075
2014-01-01	65.600
2015-01-01	66.475
2016-01-01	67.625
2017-01-01	68.675