Year Years 1990 74.7 1991 74.7 1992 74.8 1993 74.8 1994 74.8 1995 74.9 1996 75.2 1997 75.3 1998 75.4 1999 75.6 2000 75.9 2001 76.2 2002 76.6 2003 76.8 2004 76.9 2005 77.1 2006 77.4 2007 77.6 2008 77.8 2009 77.9 2010 78 2011 78.1 2012 78.2 2013 78.3