Year	Percent
1999-01-01	73.025
2000-01-01	72.700
2001-01-01	72.275
2002-01-01	72.225
2003-01-01	72.675
2004-01-01	70.250
2005-01-01	70.675
2006-01-01	71.150
2007-01-01	71.975
2008-01-01	71.975
2009-01-01	71.825
2010-01-01	71.750
2011-01-01	71.625
2012-01-01	71.700
2013-01-01	71.750
2014-01-01	71.350
2015-01-01	71.750
2016-01-01	72.400
2017-01-01	72.750