| Year | Value | | 2022 | 2.4977027817226 | | 2021 | 0.23335277939826 | | 2020 | 0.024995834027731 | | 2019 | 0.46877615938395 | | 2018 | 0.98909459802185 | | 2017 | 0.48419979612638 | | 2016 | 0.12725884448975 | | 2015 | 0.79527963057984 | | 2014 | 2.7592267135325 | | 2013 | 0.33503791218474 | | 2012 | 0.04406451044326 | | 2011 | 0.27245561610124 | | 2010 | 0.72824320751778 | | 2009 | -1.3528367295172 | | 2008 | 1.3800788616492 | | 2007 | 0.060039454498669 | | 2006 | 0.24935511607909 | | 2005 | 0.28294606876439 | | 2004 | 0.0085733882031027 | | 2003 | 0.25654181631603 | | 2002 | 0.92349402694232 | | 2001 | 0.74005550416274 | | 2000 | 0.67657868359518 | | 1999 | 0.34129692832755 | | 1998 | 0.66197419138591 | | 1997 | 1.7478045869213 | | 1996 | 0.13660035857591 | | 1995 | 0.12789904502045 | | 1994 | 0.695458057869 | | 1993 | 1.2430458970792 | | 1992 | 1.7602830605927 | | 1991 | 3.2514384875331 | | 1990 | 3.0785162869516 | | 1989 | 2.2722896206432 | | 1988 | 0.67855758045756 | | 1987 | 0.12617684169658 | | 1986 | 0.59558679945325 | | 1985 | 2.0322773460849 | | 1984 | 2.2616136919315 | | 1983 | 1.8997197134849 | | 1982 | 2.7410409556314 | | 1981 | 4.9121629182052 | | 1980 | 7.7785817655572 | | 1979 | 3.7018509254627 | | 1978 | 4.2095660106868 | | 1977 | 8.1618268959684 | | 1976 | 9.3740363860623 | | 1975 | 11.731266149871 | | 1974 | 23.222245807684 | | 1973 | 11.608623548922 | | 1972 | 4.843517138599 | | 1971 | 6.3953488372093 | | 1970 | 6.9241738348578 | | 1969 | 5.2498209110203 | | 1968 | 5.3394329573934 | | 1967 | 3.9898480888152 | | 1966 | 5.0408320588768 | | 1965 | 6.6559909426062 | | 1964 | 3.8003894530575 | | 1963 | 6.7069055639799 | | 1962 | 6.8354403481973 | | 1961 | 5.3684617848005 | | 1960 | 3.5745115253591 |
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