Year	Percent
1998-01-01	66.900
1999-01-01	65.025
2000-01-01	64.300
2001-01-01	64.325
2002-01-01	64.900
2003-01-01	64.225
2004-01-01	63.475
2005-01-01	64.275
2006-01-01	64.550
2007-01-01	65.450
2008-01-01	65.850
2009-01-01	64.325
2010-01-01	63.700
2011-01-01	63.600
2012-01-01	63.600
2013-01-01	64.050
2014-01-01	64.725
2015-01-01	65.150
2016-01-01	66.050
2017-01-01	66.950