Year	Percent
1989-01-01	12.5
1993-01-01	14.8
1995-01-01	13.5
1996-01-01	13.4
1997-01-01	12.9
1998-01-01	12.4
1999-01-01	11.5
2000-01-01	11.0
2001-01-01	11.5
2002-01-01	11.9
2003-01-01	12.2
2004-01-01	12.5
2005-01-01	13.2
2006-01-01	13.2
2007-01-01	12.9
2008-01-01	13.1
2009-01-01	14.3
2010-01-01	15.2
2011-01-01	15.8
2012-01-01	15.8
2013-01-01	15.7
2014-01-01	15.4
2015-01-01	14.6
2016-01-01	13.9