Year	Percent
1998-01-01	17.500
1999-01-01	18.550
2000-01-01	17.475
2001-01-01	16.475
2002-01-01	15.925
2003-01-01	15.300
2004-01-01	16.425
2005-01-01	15.550
2006-01-01	13.875
2007-01-01	13.050
2008-01-01	11.650
2009-01-01	13.425
2010-01-01	16.525
2011-01-01	21.700
2012-01-01	28.375
2013-01-01	31.575
2014-01-01	30.350
2015-01-01	29.150
2016-01-01	28.325
2017-01-01	26.275