| Year | Value | | 2021 | 82.5 | | 2020 | 82.648780487805 | | 2019 | 82.80487804878 | | 2018 | 82.80243902439 | | 2017 | 82.551219512195 | | 2016 | 82.407317073171 | | 2015 | 82.051219512195 | | 2014 | 82.153658536585 | | 2013 | 82.056097560976 | | 2012 | 81.704878048781 | | 2011 | 81.656097560976 | | 2010 | 81.60243902439 | | 2009 | 81.404878048781 | | 2008 | 80.951219512195 | | 2007 | 80.50487804878 | | 2006 | 80.553658536585 | | 2005 | 80.151219512195 | | 2004 | 80.146341463415 | | 2003 | 79.648780487805 | | 2002 | 79.451219512195 | | 2001 | 79.407317073171 | | 2000 | 78.953658536585 | | 1999 | 78.658536585366 | | 1998 | 78.148780487805 | | 1997 | 78 | | 1996 | 78.104878048781 | | 1995 | 77.451219512195 | | 1994 | 77.40243902439 | | 1993 | 77.153658536585 | | 1992 | 76.50487804878 | | 1991 | 76.758536585366 | | 1990 | 76.607317073171 | | 1989 | 76.307317073171 | | 1988 | 74.436585365854 | | 1987 | 75.258536585366 | | 1986 | 74.956097560976 | | 1985 | 75.207317073171 | | 1984 | 74.807317073171 | | 1983 | 74.458536585366 | | 1982 | 74.109756097561 | | 1981 | 74.260975609756 | | 1980 | 73.875609756098 | | 1979 | 73.507317073171 | | 1978 | 73.207317073171 | | 1977 | 72.958536585366 | | 1976 | 72.956097560976 | | 1975 | 72.045121951219 | | 1974 | 71.661707317073 | | 1973 | 71.693414634146 | | 1972 | 71.078048780488 | | 1971 | 71.719024390244 | | 1970 | 71.213414634146 | | 1969 | 70.970487804878 | | 1968 | 71.056585365854 | | 1967 | 71.509756097561 | | 1966 | 72.285609756098 | | 1962 | 72.112195121951 | | 1961 | 72.006585365854 |
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