Year Percent 1995-01-01 22 1996-01-01 24 1997-01-01 29 1998-01-01 32 1999-01-01 37 2000-01-01 37 2001-01-01 37 2002-01-01 34 2003-01-01 35 2004-01-01 33 2005-01-01 32 2006-01-01 32 2007-01-01 32 2008-01-01 33 2009-01-01 33 2010-01-01 33 2011-01-01 33 2012-01-01 32 2013-01-01 32