Year	Percent
1998-01-01	55.975
1999-01-01	55.900
2000-01-01	56.450
2001-01-01	56.325
2002-01-01	57.375
2003-01-01	58.500
2004-01-01	59.075
2005-01-01	59.625
2006-01-01	60.550
2007-01-01	60.875
2008-01-01	61.425
2009-01-01	60.850
2010-01-01	59.100
2011-01-01	55.100
2012-01-01	50.800
2013-01-01	48.800
2014-01-01	49.425
2015-01-01	50.800
2016-01-01	52.025
2017-01-01	53.500