Year	Percent
1989-01-01	23.1
1993-01-01	28.0
1995-01-01	25.6
1996-01-01	24.9
1997-01-01	23.2
1998-01-01	22.3
1999-01-01	20.4
2000-01-01	20.1
2001-01-01	19.6
2002-01-01	20.0
2003-01-01	21.4
2004-01-01	21.5
2005-01-01	21.5
2006-01-01	21.2
2007-01-01	21.0
2008-01-01	21.5
2009-01-01	23.5
2010-01-01	25.2
2011-01-01	26.0
2012-01-01	25.8
2013-01-01	25.1
2014-01-01	24.1
2015-01-01	23.1
2016-01-01	21.5