Year	Percent
1998-01-01	51.850
1999-01-01	52.275
2000-01-01	52.950
2001-01-01	53.525
2002-01-01	54.175
2003-01-01	54.600
2004-01-01	54.500
2005-01-01	55.300
2006-01-01	55.550
2007-01-01	55.950
2008-01-01	55.850
2009-01-01	55.675
2010-01-01	55.875
2011-01-01	54.650
2012-01-01	54.700
2013-01-01	54.125
2014-01-01	53.825
2015-01-01	53.725
2016-01-01	53.525
2017-01-01	54.075