Year	Percent
1998-01-01	55.775
1999-01-01	57.925
2000-01-01	58.300
2001-01-01	61.075
2002-01-01	61.150
2003-01-01	62.475
2004-01-01	60.300
2005-01-01	63.100
2006-01-01	64.275
2007-01-01	65.550
2008-01-01	66.000
2009-01-01	66.075
2010-01-01	66.975
2011-01-01	68.325
2012-01-01	68.750
2013-01-01	68.425
2014-01-01	70.025
2015-01-01	72.350
2016-01-01	73.575
2017-01-01	73.825