Year | Value | 2022 | 17.895153639974 | 2021 | 18.149142303914 | 2020 | 18.337389368804 | 2019 | 18.526172381378 | 2018 | 18.718553762184 | 2017 | 18.90122937583 | 2016 | 19.080574060506 | 2015 | 19.256074001106 | 2014 | 19.428918774462 | 2013 | 19.59665049059 | 2012 | 19.764121695081 | 2011 | 19.937926831627 | 2010 | 20.14762526657 | 2009 | 20.426028520627 | 2008 | 20.716038188323 | 2007 | 21.019080413272 | 2006 | 21.332943959083 | 2005 | 21.664328814863 | 2004 | 22.026904880843 | 2003 | 22.40369903289 | 2002 | 22.793133904048 | 2001 | 23.19975885601 | 2000 | 23.545522300863 | 1999 | 23.761757266818 | 1998 | 23.985917488253 | 1997 | 24.209995847427 | 1996 | 24.432115404285 | 1995 | 24.667155818334 | 1994 | 24.920345027083 | 1993 | 25.17849763564 | 1992 | 25.43423001453 | 1991 | 25.68702978908 | 1990 | 25.940767359006 | 1989 | 26.161086230304 | 1988 | 26.375062057819 | 1987 | 26.626520708238 | 1986 | 26.890309251259 | 1985 | 27.118835816665 | 1984 | 27.318362084307 | 1983 | 27.524575860857 | 1982 | 27.743945173507 | 1981 | 27.98114442856 | 1980 | 28.262929728769 | 1979 | 28.530234807784 | 1978 | 28.79749807672 | 1977 | 29.063855829077 | 1976 | 29.328966652421 | 1975 | 29.603549955503 | 1974 | 29.948155527257 | 1973 | 30.316866931301 | 1972 | 30.688394120473 | 1971 | 31.069021634413 | 1970 | 31.483682754058 | 1969 | 31.964900923725 | 1968 | 32.466112855494 | 1967 | 32.992845855316 | 1966 | 33.528656637429 | 1965 | 34.059678110822 | 1964 | 34.605137514556 | 1963 | 35.149008959667 | 1962 | 35.6947626162 | 1961 | 36.222304425099 | 1960 | 36.738013818921 |
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