| Year | Value | | 2022 | 42.473562726834 | | 2021 | 42.327747062557 | | 2020 | 42.243380154654 | | 2019 | 42.196357639522 | | 2018 | 42.223506303113 | | 2017 | 42.293868877026 | | 2016 | 42.384843655064 | | 2015 | 42.492343577099 | | 2014 | 42.615744184596 | | 2013 | 42.975534527161 | | 2012 | 43.588645271831 | | 2011 | 44.235391518 | | 2010 | 44.91599253267 | | 2009 | 45.639287525391 | | 2008 | 46.408100141592 | | 2007 | 47.225690962888 | | 2006 | 47.997302807561 | | 2005 | 48.354168159522 | | 2004 | 48.362486967746 | | 2003 | 48.369927260738 | | 2002 | 48.371446948858 | | 2001 | 48.363171889574 | | 2000 | 48.35030636409 | | 1999 | 48.350119197011 | | 1998 | 48.364110505632 | | 1997 | 48.380538209932 | | 1996 | 48.395814145641 | | 1995 | 48.391606766638 | | 1994 | 48.342790076169 | | 1993 | 48.264556936281 | | 1992 | 48.183460457647 | | 1991 | 48.094335558906 | | 1990 | 47.993172028432 | | 1989 | 47.893657341342 | | 1988 | 47.800246258761 | | 1987 | 47.69651809494 | | 1986 | 47.572062365319 | | 1985 | 47.437008556436 | | 1984 | 47.340933249452 | | 1983 | 47.277502383754 | | 1982 | 47.201228491374 | | 1981 | 47.126362259302 | | 1980 | 47.052830120022 | | 1979 | 46.974289884361 | | 1978 | 46.88415318058 | | 1977 | 46.775192368504 | | 1976 | 46.653511270242 | | 1975 | 46.531727289242 | | 1974 | 46.435974205435 | | 1973 | 46.393952867941 | | 1972 | 46.379112909382 | | 1971 | 46.364094250232 | | 1970 | 46.355573947405 | | 1969 | 46.348970050766 | | 1968 | 46.341631552189 | | 1967 | 46.315761415231 | | 1966 | 46.245619199176 | | 1965 | 46.14693112484 | | 1964 | 46.018905384182 | | 1963 | 45.863831941281 | | 1962 | 45.699248432504 | | 1961 | 45.52218153951 | | 1960 | 45.340971085652 |
|