Year Percent 1980 0.01193 1990 0.1 1991 0.2 1992 0.2 1993 0.4 1994 0.6 1995 0.7 1996 0.9 1997 0.9 1998 1 1999 1 2000 1 2001 1 2002 1 2003 1 2004 1 2005 1.1 2006 1 2007 1 2008 1 2009 1.2 2010 1.1 2011 1