Year	Percent
1998-01-01	70.500
1999-01-01	70.200
2000-01-01	69.450
2001-01-01	69.025
2002-01-01	68.975
2003-01-01	68.425
2004-01-01	68.325
2005-01-01	68.700
2006-01-01	68.525
2007-01-01	68.325
2008-01-01	68.200
2009-01-01	68.300
2010-01-01	68.050
2011-01-01	67.525
2012-01-01	67.700
2013-01-01	68.050
2014-01-01	68.200
2015-01-01	68.025
2016-01-01	68.375
2017-01-01	68.550