| Year | Value | | 2022 | 0.59326262445932 | | 2021 | 0.64123684562186 | | 2020 | 0.30288302672465 | | 2019 | 0.013502018572269 | | 2018 | 0.040500587812107 | | 2017 | 0.07285974821405 | | 2016 | 0.84246953026768 | | 2015 | 1.784046219812 | | 2014 | 1.9152049712622 | | 2013 | 2.067809862393 | | 2012 | 2.1998119199203 | | 2011 | 2.2854562083527 | | 2010 | 2.3697719150558 | | 2009 | 1.6775209368822 | | 2008 | 0.12247783583344 | | 2007 | 0.58902949388629 | | 2006 | 0.40528799708973 | | 2005 | 0.29513667601359 | | 2004 | 0.24786231551975 | | 2003 | 0.21637670338168 | | 2002 | 0.17892955568193 | | 2001 | 0.064705975235178 | | 2000 | 0.21893654962453 | | 1999 | 0.57273038619683 | | 1998 | 0.75105141360938 | | 1997 | 0.78195320476437 | | 1996 | 0.74999164858695 | | 1995 | 0.73005823579243 | | 1994 | 0.73542730744095 | | 1993 | 0.7441232692569 | | 1992 | 0.74970200224068 | | 1991 | 0.77184952844906 | | 1990 | 0.83103429914083 | | 1989 | 0.92185021561529 | | 1988 | 1.0185242007494 | | 1987 | 1.1215198257385 | | 1986 | 1.2556651924149 | | 1985 | 1.3982819494767 | | 1984 | 1.496694132615 | | 1983 | 1.4831619299241 | | 1982 | 1.0536583251609 | | 1981 | 0.76527231461116 | | 1980 | 0.89779864780814 | | 1979 | 1.052700451343 | | 1978 | 1.1781554971326 | | 1977 | 1.3195435036876 | | 1976 | 1.4546559640548 | | 1975 | 1.0317895654317 | | 1974 | 0.63537661135291 | | 1973 | 0.85215854436847 | | 1972 | 1.1273074391605 | | 1971 | 1.3911844664455 | | 1970 | 1.6409133371716 | | 1969 | 1.6640302875983 | | 1968 | 0.85540062236669 | | 1967 | 0.35715092074593 | | 1966 | 0.76157875668142 | | 1965 | 1.1182085589846 | | 1964 | 1.433399166035 | | 1963 | 1.5085138353911 | | 1962 | 0.90428444354012 | | 1961 | 0.50338748069868 |
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