Year	Percent
1998-01-01	51.350
1999-01-01	50.375
2000-01-01	50.075
2001-01-01	50.150
2002-01-01	50.475
2003-01-01	49.950
2004-01-01	49.675
2005-01-01	50.125
2006-01-01	50.575
2007-01-01	51.125
2008-01-01	51.325
2009-01-01	50.350
2010-01-01	49.725
2011-01-01	50.350
2012-01-01	50.725
2013-01-01	51.675
2014-01-01	52.125
2015-01-01	53.400
2016-01-01	54.900
2017-01-01	56.125