Year	Percent
1998-01-01	59.150
1999-01-01	60.200
2000-01-01	61.000
2001-01-01	63.575
2002-01-01	63.975
2003-01-01	65.625
2004-01-01	63.400
2005-01-01	66.300
2006-01-01	67.825
2007-01-01	69.025
2008-01-01	69.950
2009-01-01	69.350
2010-01-01	70.000
2011-01-01	70.900
2012-01-01	70.875
2013-01-01	71.600
2014-01-01	71.975
2015-01-01	74.025
2016-01-01	75.350
2017-01-01	74.950