Year	Percent
1999-01-01	42.575
2000-01-01	43.175
2001-01-01	43.125
2002-01-01	43.275
2003-01-01	44.300
2004-01-01	44.150
2005-01-01	44.200
2006-01-01	44.400
2007-01-01	44.100
2008-01-01	43.750
2009-01-01	43.050
2010-01-01	43.600
2011-01-01	43.675
2012-01-01	44.900
2013-01-01	45.375
2014-01-01	47.975
2015-01-01	49.450
2016-01-01	51.350
2017-01-01	52.075