Year	Percent
1998-01-01	30.275
1999-01-01	30.700
2000-01-01	30.975
2001-01-01	31.550
2002-01-01	31.325
2003-01-01	30.875
2004-01-01	30.575
2005-01-01	30.375
2006-01-01	30.075
2007-01-01	30.050
2008-01-01	29.800
2009-01-01	29.700
2010-01-01	29.975
2011-01-01	31.200
2012-01-01	31.825
2013-01-01	32.000
2014-01-01	32.725
2015-01-01	32.975
2016-01-01	32.775
2017-01-01	32.575