Year	Percent
1998-01-01	52.275
1999-01-01	53.025
2000-01-01	53.675
2001-01-01	52.675
2002-01-01	52.300
2003-01-01	54.800
2004-01-01	56.825
2005-01-01	57.900
2006-01-01	58.350
2007-01-01	58.675
2008-01-01	59.125
2009-01-01	61.275
2010-01-01	63.875
2011-01-01	61.825
2012-01-01	62.925
2013-01-01	64.975
2014-01-01	65.725
2015-01-01	66.500
2016-01-01	66.825
2017-01-01	66.000