Year	Percent
1998-01-01	51.525
1999-01-01	52.050
2000-01-01	52.500
2001-01-01	51.900
2002-01-01	53.450
2003-01-01	53.950
2004-01-01	53.175
2005-01-01	53.675
2006-01-01	53.425
2007-01-01	54.625
2008-01-01	54.275
2009-01-01	53.800
2010-01-01	54.300
2011-01-01	53.600
2012-01-01	53.325
2013-01-01	54.350
2014-01-01	55.275
2015-01-01	57.000
2016-01-01	58.475
2017-01-01	61.475