| Year | Value | | 2022 | 65.653328674073 | | 2021 | 64.878246005219 | | 2020 | 64.088833864595 | | 2019 | 63.273888232995 | | 2018 | 62.431195617374 | | 2017 | 61.569109854949 | | 2016 | 60.690684162328 | | 2015 | 59.804783144082 | | 2014 | 58.914506778912 | | 2013 | 58.018214377339 | | 2012 | 57.121066296004 | | 2011 | 56.225538534283 | | 2010 | 55.305439761555 | | 2009 | 54.325819384419 | | 2008 | 53.341072280732 | | 2007 | 52.353556947775 | | 2006 | 51.373220487032 | | 2005 | 50.392188382871 | | 2004 | 49.401945436133 | | 2003 | 48.424875909317 | | 2002 | 47.462225076846 | | 2001 | 46.515498826192 | | 2000 | 45.639718322338 | | 1999 | 44.889499742715 | | 1998 | 44.161987230754 | | 1997 | 43.448598898934 | | 1996 | 42.750255790418 | | 1995 | 42.06814717828 | | 1994 | 41.400424920131 | | 1993 | 40.738070395818 | | 1992 | 40.084739252432 | | 1991 | 39.430978551911 | | 1990 | 38.80736500439 | | 1989 | 38.271550417809 | | 1988 | 37.699924956692 | | 1987 | 37.108488161898 | | 1986 | 36.519976243781 | | 1985 | 35.927142804364 | | 1984 | 35.326779920796 | | 1983 | 34.724955698103 | | 1982 | 34.145908957959 | | 1981 | 33.47578330584 | | 1980 | 32.796546429449 | | 1979 | 32.115195939027 | | 1978 | 31.444600488836 | | 1977 | 30.96576990579 | | 1976 | 30.670693382039 | | 1975 | 30.390860541138 | | 1974 | 30.104663169766 | | 1973 | 29.836832699831 | | 1972 | 29.649235187233 | | 1971 | 29.53765395889 | | 1970 | 29.446453914189 | | 1969 | 29.340554186982 | | 1968 | 29.226381264146 | | 1967 | 29.103820667702 | | 1966 | 28.985449164828 | | 1965 | 28.903926511439 | | 1964 | 28.799267928243 | | 1963 | 28.223137538285 | | 1962 | 27.661470340074 | | 1961 | 27.00611550934 | | 1960 | 26.240264005136 |
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