Year	Percent
1999-01-01	72.350
2000-01-01	72.775
2001-01-01	71.150
2002-01-01	72.425
2003-01-01	73.575
2004-01-01	74.725
2005-01-01	76.800
2006-01-01	76.950
2007-01-01	78.075
2008-01-01	79.000
2009-01-01	79.250
2010-01-01	80.425
2011-01-01	78.725
2012-01-01	79.125
2013-01-01	79.750
2014-01-01	80.550
2015-01-01	80.200
2016-01-01	79.850
2017-01-01	79.600