| Year | Value | | 2022 | 33.909766417345 | | 2021 | 34.193297469316 | | 2020 | 34.439954688154 | | 2019 | 34.686830753646 | | 2018 | 34.978773001802 | | 2017 | 35.288693323784 | | 2016 | 35.6005283806 | | 2015 | 35.942629920335 | | 2014 | 36.346533516502 | | 2013 | 36.724468796987 | | 2012 | 37.068673496903 | | 2011 | 37.328150432249 | | 2010 | 37.582202682299 | | 2009 | 37.959548012344 | | 2008 | 38.390549814264 | | 2007 | 38.824647425035 | | 2006 | 39.257748207325 | | 2005 | 39.706075938608 | | 2004 | 40.1128877714 | | 2003 | 40.460709525144 | | 2002 | 40.800123122999 | | 2001 | 41.147531786407 | | 2000 | 41.516157342396 | | 1999 | 41.88549888635 | | 1998 | 42.254810658395 | | 1997 | 42.619376171837 | | 1996 | 42.968204569172 | | 1995 | 43.307572464336 | | 1994 | 43.653400882315 | | 1993 | 44.057985020655 | | 1992 | 44.497436331535 | | 1991 | 44.986224220672 | | 1990 | 45.328609656224 | | 1989 | 45.708136508679 | | 1988 | 46.090762640353 | | 1987 | 46.494716672395 | | 1986 | 46.976823472261 | | 1985 | 47.540163281368 | | 1984 | 48.101555522956 | | 1983 | 48.686884688188 | | 1982 | 49.282455526209 | | 1981 | 49.885479709581 | | 1980 | 50.505387302325 | | 1979 | 51.13519100597 | | 1978 | 51.718470628392 | | 1977 | 52.311059369158 | | 1976 | 53.004262108769 | | 1975 | 53.737149883042 | | 1974 | 54.438854163518 | | 1973 | 55.169276860625 | | 1972 | 55.924882905357 | | 1971 | 56.665746323329 | | 1970 | 57.399403666165 | | 1969 | 58.156585218779 | | 1968 | 58.903571583079 | | 1967 | 59.638594357248 | | 1966 | 60.367522631233 | | 1965 | 61.153819450484 | | 1964 | 61.989070262382 | | 1963 | 62.796454258501 | | 1962 | 63.578176288041 | | 1961 | 64.348825478225 | | 1960 | 65.10743140466 |
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