Year	Percent
1998-01-01	11.55
1999-01-01	12.65
2000-01-01	12.40
2001-01-01	12.90
2002-01-01	12.50
2003-01-01	12.40
2004-01-01	12.40
2005-01-01	12.00
2006-01-01	11.90
2007-01-01	11.60
2008-01-01	11.60
2009-01-01	12.90
2010-01-01	13.91
2011-01-01	14.19
2012-01-01	15.71
2013-01-01	16.49
2014-01-01	17.35
2015-01-01	18.26