Year Percent 1995-01-01 28 1996-01-01 28 1997-01-01 29 1998-01-01 31 1999-01-01 30 2000-01-01 33 2001-01-01 33 2002-01-01 34 2003-01-01 34 2004-01-01 32 2005-01-01 34 2006-01-01 35 2007-01-01 40 2008-01-01 37 2009-01-01 37 2010-01-01 36 2011-01-01 36 2012-01-01 36 2013-01-01 36