Year	Percent
1998-01-01	56.100
1999-01-01	56.350
2000-01-01	56.200
2001-01-01	55.625
2002-01-01	56.300
2003-01-01	57.000
2004-01-01	57.925
2005-01-01	58.175
2006-01-01	58.550
2007-01-01	58.625
2008-01-01	58.900
2009-01-01	59.650
2010-01-01	59.975
2011-01-01	59.300
2012-01-01	59.200
2013-01-01	59.125
2014-01-01	59.050
2015-01-01	59.375
2016-01-01	59.650
2017-01-01	59.575