Year Percent 1995-01-01 12 1996-01-01 15 1997-01-01 15 1998-01-01 16 1999-01-01 17 2000-01-01 17 2001-01-01 16 2002-01-01 14 2003-01-01 12 2004-01-01 14 2005-01-01 14 2006-01-01 15 2007-01-01 15 2008-01-01 15 2009-01-01 13 2010-01-01 11 2011-01-01 11 2012-01-01 12 2013-01-01 12