Year	Percent
1999-01-01	22.100
2000-01-01	21.175
2001-01-01	21.575
2002-01-01	20.750
2003-01-01	19.975
2004-01-01	19.700
2005-01-01	19.075
2006-01-01	18.750
2007-01-01	18.650
2008-01-01	18.425
2009-01-01	19.175
2010-01-01	19.350
2011-01-01	19.600
2012-01-01	19.925
2013-01-01	20.225
2014-01-01	20.450
2015-01-01	20.475
2016-01-01	20.825
2017-01-01	21.075