Year | Value | 2021 | 31.267935578331 | 2020 | 31.153733528551 | 2019 | 31.13616398243 | 2018 | 31.130307467057 | 2017 | 31.121522693997 | 2016 | 31.11859443631 | 2015 | 31.11859443631 | 2014 | 31.11859443631 | 2013 | 31.11859443631 | 2012 | 31.045387994143 | 2011 | 31.027818448023 | 2010 | 30.96925329429 | 2009 | 30.931185944363 | 2008 | 30.893118594436 | 2007 | 30.893118594436 | 2006 | 30.893118594436 | 2005 | 30.884333821376 | 2004 | 30.878477306003 | 2003 | 30.86383601757 | 2002 | 30.86383601757 | 2001 | 30.86383601757 | 2000 | 30.86383601757 | 1999 | 30.875549048316 | 1998 | 30.857979502196 | 1997 | 30.852122986823 | 1996 | 30.811127379209 | 1995 | 30.805270863836 | 1994 | 30.799414348463 | 1993 | 30.834553440703 | 1992 | 30.819912152269 | 1991 | 30.814055636896 | 1990 | 30.808199121523 | 1989 | 30.875549048316 | 1988 | 30.869692532943 | 1987 | 30.86383601757 | 1986 | 30.937042459736 | 1985 | 30.945827232796 | 1984 | 30.928257686676 | 1983 | 30.91654465593 | 1982 | 30.904831625183 | 1981 | 30.828696925329 | 1980 | 30.819912152269 | 1979 | 30.811127379209 | 1978 | 30.805270863836 | 1977 | 30.937042459736 | 1976 | 30.945827232796 | 1975 | 30.928257686676 | 1974 | 30.91654465593 | 1973 | 30.904831625183 | 1972 | 30.893118594436 | 1971 | 30.887262079063 | 1970 | 30.887262079063 | 1969 | 30.875549048316 | 1968 | 30.87262079063 | 1967 | 30.87262079063 | 1966 | 30.87262079063 | 1965 | 30.87262079063 | 1964 | 30.87262079063 | 1963 | 30.869692532943 | 1962 | 30.86383601757 | 1961 | 30.86383601757 |
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