Year | Value | 2021 | 18.343564 | 2020 | 9.830464 | 2019 | 14.624076 | 2018 | 10.89276 | 2017 | 8.56582776 | 2016 | 8.3493888 | 2015 | 7.3969052656347 | 2014 | 41.473759803594 | 2013 | 32.362596 | 2012 | 53.719716507609 | 2011 | 53.435886108005 | 2010 | 53.241236679 | 2001 | 7.364 | 2000 | 12.273 | 1999 | 13.6999998093 | 1998 | 13.5 | 1997 | 15.3000001907 | 1996 | 16.3999996185 | 1995 | 15.3000001907 | 1994 | 14.3999996185 | 1993 | 14.1999998093 | 1992 | 15.1999998093 | 1991 | 16.1000003815 | 1990 | 17.7000007629 | 1989 | 18 | 1988 | 15.8999996185 | 1987 | 16.2999992371 | 1986 | 16.5 | 1985 | 18.3999996185 | 1984 | 17.3999996185 | 1983 | 18.7000007629 | 1982 | 21 | 1981 | 21 | 1980 | 18 | 1979 | 17.1000003815 | 1978 | 14.6999998093 | 1977 | 13 | 1976 | 13.1000003815 | 1975 | 11.5 | 1974 | 10.8000001907 | 1973 | 8.3000001907 | 1972 | 8 | 1971 | 7.0999999046 | 1970 | 5.8000001907 |
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