| Year | Value | | 2015 | -190.19094758215 | | 2014 | -192.0159243904 | | 2013 | -172.43834034345 | | 2012 | -153.23717840637 | | 2011 | -143.73862049555 | | 2010 | -153.60559150443 | | 2009 | -132.23646007031 | | 2008 | -126.27199647896 | | 2007 | -134.10016623142 | | 2006 | -128.34897043021 | | 2005 | -133.66602353425 | | 2004 | -125.59655312946 | | 2003 | -127.82601877598 | | 2002 | -132.12721394128 | | 2001 | -135.64555102282 | | 2000 | -116.05070716606 | | 1999 | -101.10879794145 | | 1998 | -108.3267498704 | | 1997 | -98.472619376608 | | 1996 | -92.132942419925 | | 1995 | -101.62532675594 | | 1994 | -90.874758035983 | | 1993 | -92.354583214072 | | 1992 | -98.396847033415 | | 1991 | -96.085617657126 | | 1990 | -82.370466097494 | | 1989 | -72.074006462653 | | 1988 | -75.862788440002 | | 1987 | -91.829909794917 | | 1986 | -84.257093866134 | | 1985 | -76.554898048401 | | 1984 | -63.692977276173 | | 1983 | -53.479474543796 | | 1982 | -34.864639230143 | | 1981 | -38.697961761871 | | 1980 | -22.712162503829 | | 1979 | -27.27486595791 | | 1978 | -22.795695731539 | | 1977 | -24.062550282939 | | 1976 | -21.715838339785 | | 1975 | -24.153632384891 | | 1974 | -14.547947539386 | | 1973 | -19.156857771308 | | 1972 | -17.40751329734 | | 1971 | -4.3355503097619 | | 1970 | 6.1499335138175 | | 1969 | 16.783467951235 | | 1968 | 21.95898790822 | | 1967 | 28.339087981965 | | 1966 | 28.424041753006 | | 1965 | 28.26914986065 | | 1964 | 32.196579474516 | | 1963 | 34.465919388233 | | 1962 | 32.835980159192 | | 1961 | 30.980072863327 | | 1960 | 32.325474322359 |
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