Year Percent 1995-01-01 80 1996-01-01 80 1997-01-01 67 1998-01-01 50 1999-01-01 50 2000-01-01 56 2001-01-01 56 2002-01-01 56 2003-01-01 56 2004-01-01 63 2005-01-01 63 2006-01-01 56 2007-01-01 56 2008-01-01 60 2009-01-01 60 2010-01-01 60 2011-01-01 60 2012-01-01 60 2013-01-01 60