Year	Percent
1998-01-01	60.600
1999-01-01	59.800
2000-01-01	59.875
2001-01-01	59.425
2002-01-01	59.750
2003-01-01	60.350
2004-01-01	60.100
2005-01-01	60.300
2006-01-01	60.675
2007-01-01	60.775
2008-01-01	60.875
2009-01-01	59.575
2010-01-01	57.175
2011-01-01	52.775
2012-01-01	48.075
2013-01-01	46.000
2014-01-01	45.950
2015-01-01	46.800
2016-01-01	47.925
2017-01-01	49.275