Year	Percent
1998-01-01	11.1
1999-01-01	14.4
2000-01-01	18.4
2001-01-01	19.3
2002-01-01	17.1
2003-01-01	15.5
2004-01-01	10.3
2005-01-01	6.6
2006-01-01	4.3
2007-01-01	4.1
2008-01-01	4.2
2009-01-01	6.7
2010-01-01	8.2
2011-01-01	8.5
2012-01-01	7.7
2013-01-01	7.0
2014-01-01	5.6
2015-01-01	4.9