Year Percent 1993 1.7 1996 1.6 1997 2.4 1998 2.4 1999 2.4 2000 2.5 2001 2.6 2002 2.6 2003 2.4 2004 2.3 2005 2.3 2006 2.3 2007 2.3 2008 2.4 2009 2.6 2010 2.5 2011 2.6 2012 2.5 2013 2.6 2014 2.6 2015 2.8