Year	Percent
1989-01-01	20.2
1993-01-01	25.0
1995-01-01	22.7
1996-01-01	21.9
1997-01-01	20.2
1998-01-01	19.4
1999-01-01	17.5
2000-01-01	17.3
2001-01-01	17.6
2002-01-01	18.0
2003-01-01	19.3
2004-01-01	19.5
2005-01-01	21.0
2006-01-01	20.8
2007-01-01	20.5
2008-01-01	20.9
2009-01-01	23.0
2010-01-01	24.8
2011-01-01	25.6
2012-01-01	25.4
2013-01-01	24.5
2014-01-01	23.7
2015-01-01	22.5
2016-01-01	21.1