Year	Percent
1998-01-01	53.225
1999-01-01	55.800
2000-01-01	56.575
2001-01-01	57.500
2002-01-01	58.275
2003-01-01	57.850
2004-01-01	57.675
2005-01-01	58.625
2006-01-01	59.425
2007-01-01	60.400
2008-01-01	60.775
2009-01-01	59.775
2010-01-01	58.875
2011-01-01	59.025
2012-01-01	59.300
2013-01-01	58.625
2014-01-01	58.400
2015-01-01	58.100
2016-01-01	57.725
2017-01-01	58.125