Year | Value | 2021 | 11.739377988828 | 2020 | 11.725582273632 | 2019 | 11.682513769425 | 2018 | 11.663418479249 | 2017 | 11.598262279101 | 2016 | 11.507014232327 | 2015 | 11.393416727984 | 2014 | 11.330902403903 | 2013 | 11.270749940993 | 2012 | 11.136158935487 | 2011 | 10.962810805218 | 2010 | 10.804413648001 | 2009 | 10.711931789746 | 2008 | 10.522670087947 | 2007 | 10.442206049284 | 2006 | 10.331438888164 | 2005 | 10.244820998555 | 2004 | 10.107422429493 | 2003 | 10.118182391149 | 2002 | 9.9145259550771 | 2001 | 9.8628849421537 | 2000 | 9.7840635058824 | 1999 | 9.7959267324 | 1998 | 9.697241940641 | 1997 | 9.6606107571165 | 1996 | 9.5838397127021 | 1995 | 9.4911077652837 | 1994 | 9.2834524824082 | 1993 | 9.2196377261249 | 1992 | 9.078441619547 | 1991 | 9.0198103535178 | 1990 | 8.9290400912243 | 1989 | 8.8848565831702 | 1988 | 8.821544682289 | 1987 | 8.8056775210861 | 1986 | 8.737084831468 | 1985 | 8.7711814132015 | 1984 | 8.6758401486303 | 1983 | 8.6011447478768 | 1982 | 8.6666341845616 | 1981 | 8.5506345838424 | 1980 | 8.5821618614105 | 1979 | 8.5185460514183 | 1978 | 8.5073181812815 | 1977 | 8.4134486516663 | 1976 | 8.3924175342004 | 1975 | 8.3622400371443 | 1974 | 8.3194240639534 | 1973 | 8.348374550759 | 1972 | 8.3206451642943 | 1971 | 8.2699673200658 | 1970 | 8.2770139932378 | 1969 | 8.2449817709425 | 1968 | 8.2685538281021 | 1967 | 8.2278120009126 | 1966 | 8.1944286465931 | 1965 | 8.1763442641161 | 1964 | 8.0934055444804 | 1963 | 8.0265141159622 | 1962 | 7.929191036931 | 1961 | 7.8816727629744 |
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