Year	Percent
1998-01-01	19.5
1999-01-01	18.8
2000-01-01	21.6
2001-01-01	21
2002-01-01	21.4
2003-01-01	24.2
2004-01-01	23.6
2005-01-01	20.9
2006-01-01	20.9
2007-01-01	20.9
2008-01-01	20.9
2009-01-01	13.2
2010-01-01	13.0
2011-01-01	11.3
2012-01-01	12.8
2013-01-01	14.5
2014-01-01	13.8
2015-01-01	14.5