Year	Percent
1998-01-01	10.4
1999-01-01	10.6
2000-01-01	9.8
2001-01-01	11.4
2002-01-01	12.2
2003-01-01	12.3
2004-01-01	12.8
2005-01-01	12.8
2006-01-01	15.1
2007-01-01	12.7
2008-01-01	12.7
2009-01-01	15.8
2010-01-01	21.1
2011-01-01	21.6
2012-01-01	25
2013-01-01	26.2
2014-01-01	28.5
2015-01-01	28.2