Year	Percent
1998-01-01	31.300
1999-01-01	30.275
2000-01-01	29.775
2001-01-01	29.550
2002-01-01	30.075
2003-01-01	30.325
2004-01-01	30.750
2005-01-01	30.675
2006-01-01	30.200
2007-01-01	30.000
2008-01-01	29.350
2009-01-01	30.950
2010-01-01	30.925
2011-01-01	30.675
2012-01-01	31.075
2013-01-01	31.800
2014-01-01	31.975
2015-01-01	31.975
2016-01-01	31.875
2017-01-01	31.350