Year	Percent
1998-01-01	7.0
1999-01-01	6.8
2000-01-01	6.2
2001-01-01	6.2
2002-01-01	7.2
2003-01-01	7.1
2004-01-01	7.1
2005-01-01	7.4
2006-01-01	7.8
2007-01-01	10.9
2008-01-01	12.4
2009-01-01	14.9
2010-01-01	19
2011-01-01	15.5
2012-01-01	17.9
2013-01-01	18.7
2014-01-01	20.3
2015-01-01	21.1