Year	Percent
1998-01-01	20.675
1999-01-01	20.850
2000-01-01	20.750
2001-01-01	20.375
2002-01-01	19.950
2003-01-01	20.475
2004-01-01	21.100
2005-01-01	21.150
2006-01-01	20.800
2007-01-01	20.775
2008-01-01	20.750
2009-01-01	21.800
2010-01-01	22.125
2011-01-01	22.050
2012-01-01	22.725
2013-01-01	23.500
2014-01-01	23.300
2015-01-01	23.350
2016-01-01	22.825
2017-01-01	22.075