Year	Percent
1998-01-01	50.950
1999-01-01	49.675
2000-01-01	49.500
2001-01-01	50.200
2002-01-01	48.800
2003-01-01	47.725
2004-01-01	45.850
2005-01-01	45.550
2006-01-01	45.050
2007-01-01	45.150
2008-01-01	44.975
2009-01-01	43.525
2010-01-01	42.500
2011-01-01	42.550
2012-01-01	41.725
2013-01-01	41.700
2014-01-01	41.000
2015-01-01	40.075
2016-01-01	39.550
2017-01-01	39.750