Year	Percent
1999-01-01	18.475
2000-01-01	17.125
2001-01-01	16.075
2002-01-01	16.125
2003-01-01	15.175
2004-01-01	15.900
2005-01-01	17.875
2006-01-01	18.800
2007-01-01	19.325
2008-01-01	17.875
2009-01-01	19.250
2010-01-01	19.125
2011-01-01	19.600
2012-01-01	19.625
2013-01-01	19.475
2014-01-01	19.625
2015-01-01	19.225
2016-01-01	18.550
2017-01-01	20.200