| Year | Value | | 2022 | 0.9079145243433 | | 2021 | 0.91177674914823 | | 2020 | 0.35893266190288 | | 2019 | 0.73928347132306 | | 2018 | 0.80023059696777 | | 2017 | 0.76851387761496 | | 2016 | 0.61936634533248 | | 2015 | 0.85119791108699 | | 2014 | 0.70237095053605 | | 2013 | 0.40198253585844 | | 2012 | 1.1039579972368 | | 2011 | 0.67254329181863 | | 2010 | 0.73444639633811 | | 2009 | 0.215353334345 | | 2008 | 0.59823878694972 | | 2007 | 0.85963327221703 | | 2006 | 0.64227048287613 | | 2005 | 0.43687140610588 | | 2004 | 0.77991856230718 | | 2003 | 0.19740412647212 | | 2002 | 0.44284682728195 | | 2001 | 0.73696266813843 | | 2000 | 0.88159407585375 | | 1999 | 0.95512581433174 | | 1998 | 0.83480880733887 | | 1997 | 0.83251285481332 | | 1996 | 4.438607794811 | | 1995 | 1.9801327772975 | | 1994 | 2.2520304311179 | | 1993 | 1.7177707341707 | | 1992 | 0.83965003145788 | | 1991 | 0.82922833644585 | | 1990 | 0.32131503322199 | | 1989 | 1.0359123201146 | | 1988 | 0.84046854072885 | | 1987 | 1.0067531520737 | | 1986 | 1.2458269832087 | | 1985 | 1.0742587716364 | | 1984 | 0.98297356685487 | | 1983 | 1.519407906122 | | 1982 | 1.552496270392 | | 1981 | 2.3482267682345 | | 1980 | 2.6700809652344 | | 1979 | 5.4654537842327 | | 1978 | 1.8117064189099 | | 1977 | 1.443711419883 | | 1976 | 1.2561971952605 | | 1975 | 1.896113099629 | | 1974 | 3.1605758544293 | | 1973 | 2.8213988312531 | | 1972 | 1.9170854843184 | | 1971 | 2.1564245272915 | | 1970 | 2.4314432025797 | | 1969 | 1.5965695354384 | | 1968 | 2.1235267414394 | | 1967 | 2.5270973641484 | | 1966 | 0.88547577642861 | | 1965 | 2.6273950631466 | | 1964 | 2.4172716942896 | | 1963 | 3.4406688504393 | | 1962 | 4.2364946734332 | | 1961 | 1.7008510426643 |
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