Year	Percent
1991-01-01	6.8
1992-01-01	7.3
1993-01-01	7.5
1994-01-01	7.4
1995-01-01	7.2
1996-01-01	7.1
1997-01-01	7.0
1998-01-01	6.8
1999-01-01	6.5
2000-01-01	6.0
2001-01-01	6.0
2002-01-01	6.5
2003-01-01	6.6
2004-01-01	6.4
2005-01-01	6.3
2006-01-01	5.9
2007-01-01	5.5
2008-01-01	5.8
2009-01-01	7.4
2010-01-01	7.6
2011-01-01	7.4
2012-01-01	7.3
2013-01-01	6.9
2014-01-01	6.3
2015-01-01	5.6
2016-01-01	5.3