Year	Percent
1998-01-01	60.325
1999-01-01	58.900
2000-01-01	58.450
2001-01-01	58.550
2002-01-01	59.050
2003-01-01	58.500
2004-01-01	58.050
2005-01-01	58.750
2006-01-01	59.175
2007-01-01	60.025
2008-01-01	60.350
2009-01-01	59.100
2010-01-01	58.500
2011-01-01	58.825
2012-01-01	59.050
2013-01-01	59.850
2014-01-01	60.450
2015-01-01	61.350
2016-01-01	62.725
2017-01-01	63.850