Year	Percent
1998-01-01	32.775
1999-01-01	32.950
2000-01-01	33.350
2001-01-01	33.050
2002-01-01	33.775
2003-01-01	34.625
2004-01-01	35.175
2005-01-01	35.650
2006-01-01	36.600
2007-01-01	36.900
2008-01-01	37.550
2009-01-01	37.725
2010-01-01	36.900
2011-01-01	34.375
2012-01-01	31.575
2013-01-01	30.025
2014-01-01	30.800
2015-01-01	31.850
2016-01-01	32.375
2017-01-01	33.050