Year	Percent
1999-01-01	46.475
2000-01-01	45.975
2001-01-01	46.300
2002-01-01	45.925
2003-01-01	46.750
2004-01-01	45.775
2005-01-01	45.850
2006-01-01	46.775
2007-01-01	47.850
2008-01-01	49.275
2009-01-01	47.600
2010-01-01	47.100
2011-01-01	47.225
2012-01-01	47.225
2013-01-01	47.575
2014-01-01	48.175
2015-01-01	49.525
2016-01-01	51.400
2017-01-01	53.025