Year	Percent
1999-01-01	50.350
2000-01-01	51.475
2001-01-01	50.950
2002-01-01	51.400
2003-01-01	51.825
2004-01-01	52.650
2005-01-01	53.800
2006-01-01	53.975
2007-01-01	55.300
2008-01-01	56.150
2009-01-01	55.975
2010-01-01	56.525
2011-01-01	56.675
2012-01-01	56.775
2013-01-01	57.175
2014-01-01	57.950
2015-01-01	58.025
2016-01-01	58.100
2017-01-01	58.700