| Year | Value | | 2022 | 31.255895104902 | | 2021 | 9.9710886750444 | | 2020 | 9.8872895626994 | | 2019 | 7.1436400333086 | | 2018 | 7.808765166107 | | 2017 | 12.371921550705 | | 2016 | 17.454634707087 | | 2015 | 17.149969500788 | | 2014 | 15.489616033332 | | 2013 | 11.666192307173 | | 2012 | 11.186340944107 | | 2011 | 8.7284593709302 | | 2010 | 10.733389835492 | | 2009 | 19.246948222086 | | 2008 | 16.494639613412 | | 2007 | 10.734266545629 | | 2006 | 11.679183939249 | | 2005 | 15.438992015591 | | 2004 | 18.042738823256 | | 2003 | 29.772979716038 | | 2002 | 9.3609323956031 | | 2001 | 41.509496287803 | | 2000 | 40.240933123914 | | 1999 | 4.8653978507753 | | 1998 | 14.624166666668 | | 1997 | 27.885208640753 | | 1996 | 46.561019676228 | | 1995 | 59.461553699145 | | 1994 | 24.870255436958 | | 1993 | 24.95984247425 | | 1992 | 10.056116744884 | | 1991 | 18.031439008985 | | 1990 | 37.259066485567 | | 1989 | 25.223692029583 | | 1988 | 31.359267626477 | | 1987 | 39.815067877536 | | 1986 | 24.5654160765 | | 1985 | 10.305440669829 | | 1984 | 39.665313794727 | | 1983 | 122.87451457259 | | 1982 | 22.295566408089 | | 1981 | 116.50360399654 | | 1980 | 50.070139343636 | | 1979 | 54.441288334562 | | 1978 | 73.091666667343 | | 1977 | 116.45021645364 | | 1976 | 56.081081082976 | | 1975 | 29.824561404817 | | 1974 | 18.134715026846 | | 1973 | 17.682926823171 | | 1972 | 10.067114093959 | | 1971 | 9.5588235374677 | | 1970 | 3.0303030305327 | | 1969 | 7.3170731626013 | | 1968 | 7.8947368421054 | | 1967 | -8.4224858978028 | | 1966 | 13.237885462654 | | 1965 | 26.444784849017 |
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