| Year | Value | | 2017 | 78.017073170732 | | 2016 | 77.719512195122 | | 2015 | 78.075609756098 | | 2014 | 77.975609756098 | | 2013 | 77.826829268293 | | 2012 | 77.524390243902 | | 2011 | 77.473170731707 | | 2009 | 76.156097560976 | | 2008 | 75.309756097561 | | 2007 | 75.363414634146 | | 2006 | 74.709756097561 | | 2005 | 73.565707317073 | | 2004 | 73.428926829268 | | 2003 | 73.353512195122 | | 2002 | 73.211536585366 | | 2001 | 73.110756097561 | | 2000 | 73.033951219512 | | 1999 | 72.93756097561 | | 1998 | 72.858317073171 | | 1997 | 72.753365853659 | | 1996 | 72.692829268293 | | 1995 | 72.601341463415 | | 1994 | 72.590073170732 | | 1993 | 72.498073170732 | | 1992 | 72.418073170732 | | 1991 | 72.349707317073 | | 1990 | 72.250390243902 | | 1989 | 71.948658536585 | | 1988 | 72.042804878049 | | 1987 | 71.951048780488 | | 1986 | 71.743975609756 | | 1985 | 71.626756097561 | | 1984 | 71.339926829268 | | 1983 | 71.276097560976 | | 1982 | 71.14787804878 | | 1981 | 71.024146341463 | | 1980 | 70.894682926829 | | 1979 | 70.744097560976 | | 1978 | 70.445341463415 | | 1977 | 70.154951219512 | | 1976 | 70.028073170732 | | 1975 | 69.648536585366 | | 1974 | 69.529024390244 | | 1973 | 69.192195121951 | | 1972 | 68.790365853658 | | 1971 | 68.460853658537 | | 1970 | 68.278146341463 | | 1969 | 67.944317073171 | | 1968 | 67.65843902439 | | 1967 | 67.491487804878 | | 1966 | 67.198609756098 | | 1965 | 66.906219512195 | | 1964 | 66.667585365854 | | 1963 | 66.474317073171 | | 1962 | 66.199024390244 | | 1961 | 65.909292682927 | | 1960 | 65.778024390244 |
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