Year	Percent
1998-01-01	52.825
1999-01-01	53.875
2000-01-01	54.800
2001-01-01	55.500
2002-01-01	55.625
2003-01-01	55.500
2004-01-01	55.450
2005-01-01	55.675
2006-01-01	55.850
2007-01-01	56.025
2008-01-01	56.550
2009-01-01	55.700
2010-01-01	55.075
2011-01-01	53.650
2012-01-01	52.225
2013-01-01	51.425
2014-01-01	52.700
2015-01-01	53.825
2016-01-01	54.650
2017-01-01	56.450