Year	Percent
1999-01-01	52.975
2000-01-01	53.375
2001-01-01	52.775
2002-01-01	52.975
2003-01-01	53.825
2004-01-01	53.775
2005-01-01	54.400
2006-01-01	55.025
2007-01-01	54.700
2008-01-01	54.300
2009-01-01	54.275
2010-01-01	54.825
2011-01-01	55.225
2012-01-01	56.325
2013-01-01	56.975
2014-01-01	58.675
2015-01-01	59.950
2016-01-01	61.075
2017-01-01	61.825