| Year | Value | | 2022 | 8.3954829799337 | | 2021 | 2.446088671755 | | 2020 | 0.63842279797954 | | 2019 | 0.25037099675879 | | 2018 | 1.4354911953176 | | 2017 | 0.53176649617447 | | 2016 | -1.4291666666667 | | 2015 | -2.0969976905313 | | 2014 | -1.354988854463 | | 2013 | 0.39935767646405 | | 2012 | 2.3890541004228 | | 2011 | 3.2894493956421 | | 2010 | 2.4300408410225 | | 2009 | 0.32627665224979 | | 2008 | 4.6690084190248 | | 2007 | 2.3726518366972 | | 2006 | 2.3046873297856 | | 2005 | 2.5601613233023 | | 2004 | 2.2862170680168 | | 2003 | 4.1390653868686 | | 2002 | 2.8011550518075 | | 2001 | 1.9730419172991 | | 2000 | 4.1416576470205 | | 1999 | 1.63 | | 1998 | 2.2277073265432 | | 1997 | 3.6053444436463 | | 1996 | 2.9789248648127 | | 1995 | 2.6158178795634 | | 1994 | 4.6985893105498 | | 1993 | 4.8541666666669 | | 1992 | 6.5102195306582 | | 1991 | 5.0352743884811 | | 1990 | 4.5020546289584 | | 1989 | 3.7654804828339 | | 1988 | 3.4292663153629 | | 1987 | 2.791666666667 | | 1986 | 1.2183692596766 | | 1985 | 5.034453663648 | | 1984 | 5.9919511104844 | | 1983 | 5.0497142410088 | | 1982 | 6.4327972669369 | | 1981 | 10.744693608398 | | 1980 | 13.517560577258 | | 1979 | 9.4637082951902 | | 1978 | 7.4362832989466 | | 1977 | 7.3264604810132 | | 1976 | 3.8543897216273 | | 1975 | 4.6394858404655 | | 1974 | 16.1766666665 | | 1973 | 7.8088823405226 | | 1972 | 4.8323036186565 | | 1971 | 4.1440061282546 | | 1970 | 2.4001882503169 | | 1969 | 2.3851590101302 | | 1968 | 3.766666666167 | | 1967 | 0.70493454280659 | | 1966 | 0.50607287449889 | | 1965 | 0.20283975659441 | | 1964 | 0.30333670475254 | | 1963 | 1.9587628865985 | | 1962 | 0.10319917440631 | | 1961 | 0.61538461538495 | | 1960 | 0.82730093071395 |
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