Year	Percent
1998-01-01	36.675
1999-01-01	37.800
2000-01-01	38.575
2001-01-01	38.450
2002-01-01	38.625
2003-01-01	39.125
2004-01-01	39.525
2005-01-01	39.250
2006-01-01	38.975
2007-01-01	38.775
2008-01-01	38.525
2009-01-01	39.500
2010-01-01	40.050
2011-01-01	40.075
2012-01-01	40.250
2013-01-01	40.850
2014-01-01	41.050
2015-01-01	41.050
2016-01-01	41.375
2017-01-01	41.125