Year	Percent
1998-01-01	61.175
1999-01-01	61.650
2000-01-01	61.600
2001-01-01	63.400
2002-01-01	64.525
2003-01-01	65.425
2004-01-01	63.775
2005-01-01	66.150
2006-01-01	67.675
2007-01-01	69.175
2008-01-01	69.250
2009-01-01	71.175
2010-01-01	71.900
2011-01-01	72.900
2012-01-01	71.450
2013-01-01	72.875
2014-01-01	72.875
2015-01-01	73.800
2016-01-01	73.400
2017-01-01	73.825