Year | Value | 2021 | 20.142048960419 | 2020 | 20.599688213105 | 2019 | 21.058566234051 | 2018 | 21.887914742788 | 2017 | 22.555494608502 | 2016 | 23.045558378472 | 2015 | 24.015800352169 | 2014 | 24.538066197945 | 2013 | 24.78552173223 | 2012 | 24.825997797087 | 2011 | 24.682374481759 | 2010 | 24.534705684716 | 2009 | 24.296845334905 | 2008 | 24.261039903509 | 2007 | 24.208327721909 | 2006 | 24.048330356362 | 2005 | 24.0077959385 | 2004 | 24.070446317312 | 2003 | 24.192452258613 | 2002 | 24.294332494285 | 2001 | 24.580134111776 | 2000 | 24.831398903155 | 1999 | 25.143703662252 | 1998 | 25.54881340493 | 1997 | 26.040787784148 | 1996 | 26.766007658296 | 1995 | 27.855089022535 | 1994 | 29.087828776912 | 1993 | 30.379739657616 | 1992 | 31.529791726739 | 1991 | 32.470217189195 | 1990 | 33.404663877189 | 1989 | 34.403774692216 | 1988 | 35.603450774213 | 1987 | 36.736949867974 | 1986 | 37.884447491041 | 1985 | 38.905006550919 | 1984 | 39.706187265223 | 1983 | 40.399946736255 | 1982 | 40.89741720109 | 1981 | 41.140526525981 | 1980 | 41.61031574263 | 1979 | 41.916058224056 | 1978 | 41.86843686688 | 1977 | 42.012782959721 | 1976 | 42.284150057869 | 1975 | 42.389348069495 | 1974 | 42.489108304312 | 1973 | 42.681978215355 | 1972 | 43.138831549869 | 1971 | 43.657300607702 | 1970 | 44.061848889482 | 1969 | 44.522904902568 | 1968 | 44.877184326557 | 1967 | 45.280829266245 | 1966 | 45.67902201756 | 1965 | 46.018612296544 | 1964 | 46.479942711308 | 1963 | 46.896312086657 | 1962 | 47.348532330071 | 1961 | 47.187300382115 | 1960 | 47.477953323521 |
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