Year % 1985 76.56579 1986 76.36163 1987 77.74956 1988 74.58691 1989 75.44092 1990 76.46917 1991 77.61996 1992 78.86578 1993 80.20862 1994 81.41593 1995 82.45047 1996 83.61537 1997 84.81287 1998 86.03632 1999 87.11207 2000 87.07454 2001 89.05893 2002 90.67937 2003 88.0376 2004 87.49954 2005 89.19637 2006 90.65608 2007 90.67895 2008 91.02425 2009 91.55576 2010 91.99801 2011 92.14565 2012 90.59078 2013 90.81557 2016 90.83289 2017 91.91673