Year	Percent
1999-01-01	27.900
2000-01-01	28.300
2001-01-01	27.850
2002-01-01	28.075
2003-01-01	28.050
2004-01-01	27.475
2005-01-01	27.950
2006-01-01	27.575
2007-01-01	28.000
2008-01-01	27.775
2009-01-01	28.500
2010-01-01	29.525
2011-01-01	29.950
2012-01-01	30.750
2013-01-01	31.600
2014-01-01	31.675
2015-01-01	31.525
2016-01-01	29.925
2017-01-01	31.175