Year	Percent
1998-01-01	51.300
1999-01-01	51.200
2000-01-01	51.500
2001-01-01	52.450
2002-01-01	52.900
2003-01-01	48.950
2004-01-01	47.300
2005-01-01	46.025
2006-01-01	45.525
2007-01-01	44.675
2008-01-01	43.600
2009-01-01	40.100
2010-01-01	37.975
2011-01-01	40.400
2012-01-01	39.225
2013-01-01	36.225
2014-01-01	34.750
2015-01-01	34.225
2016-01-01	35.025
2017-01-01	35.550