Year	Percent
1998-01-01	32.125
1999-01-01	32.875
2000-01-01	33.400
2001-01-01	33.350
2002-01-01	33.925
2003-01-01	34.325
2004-01-01	34.900
2005-01-01	35.025
2006-01-01	34.750
2007-01-01	34.650
2008-01-01	34.150
2009-01-01	35.725
2010-01-01	35.850
2011-01-01	35.725
2012-01-01	36.225
2013-01-01	37.025
2014-01-01	37.400
2015-01-01	37.525
2016-01-01	37.575
2017-01-01	37.275