Year	Percent
1998-01-01	37.250
1999-01-01	38.275
2000-01-01	39.550
2001-01-01	41.100
2002-01-01	42.025
2003-01-01	42.650
2004-01-01	45.450
2005-01-01	45.375
2006-01-01	46.350
2007-01-01	46.625
2008-01-01	47.250
2009-01-01	46.350
2010-01-01	46.125
2011-01-01	46.500
2012-01-01	47.075
2013-01-01	46.525
2014-01-01	46.825
2015-01-01	47.175
2016-01-01	48.075
2017-01-01	48.900