Year	Percent
1998-01-01	47.825
1999-01-01	48.075
2000-01-01	48.325
2001-01-01	48.575
2002-01-01	48.850
2003-01-01	49.175
2004-01-01	49.575
2005-01-01	49.100
2006-01-01	49.075
2007-01-01	48.750
2008-01-01	49.100
2009-01-01	48.475
2010-01-01	48.225
2011-01-01	48.150
2012-01-01	49.100
2013-01-01	48.800
2014-01-01	49.075
2015-01-01	48.950
2016-01-01	49.525
2017-01-01	49.825