Year	Percent
1998-01-01	34.800
1999-01-01	35.325
2000-01-01	35.775
2001-01-01	36.375
2002-01-01	36.775
2003-01-01	37.075
2004-01-01	38.550
2005-01-01	38.075
2006-01-01	38.200
2007-01-01	37.925
2008-01-01	38.650
2009-01-01	38.225
2010-01-01	38.150
2011-01-01	38.400
2012-01-01	39.700
2013-01-01	39.675
2014-01-01	40.100
2015-01-01	39.775
2016-01-01	40.450
2017-01-01	40.925