Year	Percent
1998-01-01	32.300
1999-01-01	33.175
2000-01-01	34.250
2001-01-01	35.550
2002-01-01	36.350
2003-01-01	36.925
2004-01-01	39.200
2005-01-01	39.050
2006-01-01	39.850
2007-01-01	40.125
2008-01-01	40.700
2009-01-01	40.000
2010-01-01	39.875
2011-01-01	40.225
2012-01-01	40.625
2013-01-01	40.100
2014-01-01	40.325
2015-01-01	40.650
2016-01-01	41.400
2017-01-01	42.175