Year Percent 1995-01-01 14 1996-01-01 14 1997-01-01 13 1998-01-01 13.5 1999-01-01 15.5 2000-01-01 17 2001-01-01 21 2002-01-01 28 2003-01-01 28 2004-01-01 30.5 2005-01-01 31.5 2006-01-01 33 2007-01-01 33 2008-01-01 37.5 2009-01-01 38 2010-01-01 38 2011-01-01 37.5 2012-01-01 37 2013-01-01 35.5