Year	Percent
1998-01-01	36.025
1999-01-01	35.875
2000-01-01	36.400
2001-01-01	36.825
2002-01-01	37.275
2003-01-01	37.450
2004-01-01	37.800
2005-01-01	37.600
2006-01-01	37.675
2007-01-01	38.525
2008-01-01	38.950
2009-01-01	38.525
2010-01-01	38.475
2011-01-01	37.800
2012-01-01	36.500
2013-01-01	34.925
2014-01-01	34.400
2015-01-01	33.525
2016-01-01	32.375
2017-01-01	31.325