| Year | Value | | 2021 | 11.20987654321 | | 2020 | 11.259259259259 | | 2019 | 11.314128943759 | | 2018 | 11.363511659808 | | 2017 | 11.415637860082 | | 2016 | 11.478737997257 | | 2015 | 11.536351165981 | | 2014 | 11.582990397805 | | 2013 | 11.626886145405 | | 2012 | 11.648834019204 | | 2011 | 11.670781893004 | | 2010 | 11.747599451303 | | 2009 | 11.780521262003 | | 2008 | 11.818930041152 | | 2007 | 11.868312757202 | | 2006 | 11.914951989026 | | 2005 | 11.961591220851 | | 2004 | 12.013717421125 | | 2003 | 12.063100137174 | | 2002 | 12.123456790123 | | 2001 | 12.192043895748 | | 2000 | 12.274348422497 | | 1999 | 12.353909465021 | | 1998 | 12.441700960219 | | 1997 | 12.534979423868 | | 1996 | 12.625514403292 | | 1995 | 12.69884805266 | | 1994 | 12.781130005485 | | 1993 | 12.849698299506 | | 1992 | 12.92923752057 | | 1991 | 13.000548546352 | | 1990 | 13.077345035655 | | 1989 | 13.143170597915 | | 1988 | 13.181568842567 | | 1987 | 13.203510696654 | | 1986 | 13.216342199068 | | 1985 | 13.247394404827 | | 1984 | 13.260213874417 | | 1983 | 13.225013653741 | | 1982 | 13.249590387766 | | 1981 | 13.26692139738 | | 1980 | 13.306033306033 | | 1979 | 13.32423580786 | | 1978 | 13.367903930131 | | 1977 | 13.403384279476 | | 1976 | 13.427012278308 | | 1975 | 13.492496589359 | | 1974 | 13.578832515003 | | 1973 | 13.679759956356 | | 1972 | 13.794326241135 | | 1971 | 13.97600218162 | | 1970 | 14.169620943551 | | 1969 | 14.076902099809 | | 1968 | 14.507772020725 | | 1967 | 14.663212435233 | | 1966 | 14.870466321243 | | 1965 | 14.938641941642 | | 1964 | 15.08044723207 | | 1963 | 15.189528224707 | | 1962 | 15.325879465503 | | 1961 | 15.43496045814 |
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