Year	Percent
1999-01-01	51.900
2000-01-01	52.950
2001-01-01	52.325
2002-01-01	53.900
2003-01-01	55.150
2004-01-01	56.025
2005-01-01	57.125
2006-01-01	57.950
2007-01-01	58.575
2008-01-01	59.375
2009-01-01	59.500
2010-01-01	59.600
2011-01-01	59.675
2012-01-01	59.775
2013-01-01	59.375
2014-01-01	58.950
2015-01-01	58.825
2016-01-01	58.525
2017-01-01	58.125