Year	Percent
1998-01-01	38.300
1999-01-01	37.850
2000-01-01	36.250
2001-01-01	37.100
2002-01-01	36.500
2003-01-01	34.350
2004-01-01	32.075
2005-01-01	30.775
2006-01-01	30.650
2007-01-01	30.150
2008-01-01	30.350
2009-01-01	29.150
2010-01-01	25.975
2011-01-01	24.500
2012-01-01	21.200
2013-01-01	20.375
2014-01-01	21.875
2015-01-01	21.500
2016-01-01	22.250
2017-01-01	24.075