Year	Percent
1984-01-01	18.0
1985-01-01	16.6
1986-01-01	16.8
1987-01-01	13.9
1988-01-01	11.9
1989-01-01	9.8
1990-01-01	9.7
1991-01-01	13.6
1992-01-01	15.9
1993-01-01	17.1
1994-01-01	15.6
1995-01-01	14.8
1996-01-01	13.8
1997-01-01	12.4
1998-01-01	11.4
1999-01-01	10.7
2000-01-01	9.9
2001-01-01	9.7
2002-01-01	9.7
2003-01-01	9.4
2004-01-01	9.1
2005-01-01	9.8
2006-01-01	10.6
2007-01-01	10.5
2008-01-01	11.6
2009-01-01	15.3
2010-01-01	15.3
2011-01-01	16.5
2012-01-01	16.9