Year Percent 1996 6.3 2001 10.5 2002 6.9 2003 4.6 2004 2.3 2005 6.9 2006 0.6 2007 0.3 2008 0.1 2009 0.2 2010 0.1 2011 0 2012 0 2013 0 2014 0 2015 0