Year	Percent
1999-01-01	80.875
2000-01-01	80.775
2001-01-01	80.225
2002-01-01	79.975
2003-01-01	79.675
2004-01-01	79.700
2005-01-01	79.850
2006-01-01	81.225
2007-01-01	80.775
2008-01-01	81.575
2009-01-01	77.975
2010-01-01	75.575
2011-01-01	75.850
2012-01-01	75.175
2013-01-01	75.000
2014-01-01	75.775
2015-01-01	76.575
2016-01-01	77.725
2017-01-01	76.850