Year	Percent
1998-01-01	47.650
1999-01-01	46.625
2000-01-01	46.175
2001-01-01	46.200
2002-01-01	46.325
2003-01-01	45.775
2004-01-01	45.525
2005-01-01	45.700
2006-01-01	46.100
2007-01-01	46.425
2008-01-01	46.550
2009-01-01	45.675
2010-01-01	45.150
2011-01-01	45.550
2012-01-01	45.925
2013-01-01	46.700
2014-01-01	47.075
2015-01-01	48.125
2016-01-01	49.425
2017-01-01	50.425