Year | Value | 2021 | 8.3022865275455 | 2020 | 7.1556654039416 | 2019 | 6.4637230872163 | 2018 | 6.4470933144606 | 2017 | 6.4523289916701 | 2016 | 6.4898187721615 | 2015 | 6.5384038476783 | 2014 | 6.6147845122191 | 2013 | 6.7174241126799 | 2012 | 6.8131879819074 | 2011 | 6.9124306463423 | 2010 | 7.0347680152393 | 2009 | 7.1090964830476 | 2008 | 7.2450171929201 | 2007 | 7.2664765635991 | 2006 | 7.3344644139496 | 2005 | 7.4598074770678 | 2004 | 7.5987199166327 | 2003 | 7.6601971773441 | 2002 | 7.7467835276873 | 2001 | 7.885509502156 | 2000 | 7.9768547561977 | 1999 | 8.098496887158 | 1998 | 8.2612617896448 | 1997 | 8.43115437693 | 1996 | 8.6137849407527 | 1995 | 8.7599738502494 | 1994 | 9.1786217349516 | 1993 | 9.1014659116908 | 1992 | 9.2579754853881 | 1991 | 9.5237672042356 | 1990 | 9.7016110726448 | 1989 | 9.9212855594106 | 1988 | 10.171614364965 | 1987 | 10.408065115898 | 1986 | 10.815731523639 | 1985 | 11.090959572565 | 1984 | 11.409852841154 | 1983 | 11.740597365867 | 1982 | 11.920633096124 | 1981 | 12.204009222819 | 1980 | 12.466171493929 | 1979 | 12.75916183783 | 1978 | 13.1218827554 | 1977 | 13.445393118388 | 1976 | 14.010053171258 | 1975 | 14.379269126577 | 1974 | 14.448537573282 | 1973 | 14.745136641251 | 1972 | 15.068569542963 | 1971 | 16.715293942927 | 1970 | 15.954334386204 | 1969 | 15.930606773239 | 1968 | 16.221026698386 | 1967 | 16.982245541044 | 1966 | 17.462200745694 | 1965 | 18.166737732439 | 1964 | 17.478707372369 | 1963 | 17.84675791032 | 1962 | 18.206040014806 | 1961 | 18.542119879229 | 1960 | 18.902972107165 |
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