| Year | Value | | 2014 | -32.970794069021 | | 2013 | -39.819801641183 | | 2012 | -46.283535358393 | | 2011 | -58.246368257011 | | 2010 | -60.893736531026 | | 2009 | -54.00433127983 | | 2008 | -50.047787639434 | | 2007 | -50.719291654234 | | 2006 | -50.495399680439 | | 2005 | -49.552070074812 | | 2004 | -36.434979760859 | | 2003 | -30.379850556193 | | 2002 | -26.829877786286 | | 2001 | -26.401629234295 | | 2000 | -20.064012262048 | | 1999 | -9.8515019790179 | | 1998 | 1.9921375779591 | | 1997 | 7.519481467709 | | 1996 | 7.7867406937657 | | 1995 | 6.8605117212035 | | 1994 | 4.0583142298111 | | 1993 | 3.175987347296 | | 1992 | 0.20282967765495 | | 1991 | 0.19541083077457 | | 1990 | 0.2397042308794 | | 1989 | 0.20428975575462 | | 1988 | 0.20973065388172 | | 1987 | -1.4690233911333 | | 1986 | 0.02980295173214 | | 1985 | 0.98318780157119 | | 1984 | -2.0535827428845 | | 1983 | -1.1056064814787 | | 1982 | 0.0208706505554 | | 1981 | 0.89099567325143 | | 1980 | 0.98343740783127 | | 1979 | 0.42134813075242 | | 1978 | 0.13726561903891 | | 1977 | 0.48919657565777 | | 1976 | 1.8712608607614 | | 1975 | 2.9561624089588 | | 1974 | 4.56973499005 | | 1973 | 1.3136104001609 | | 1972 | 5.1427300628911 | | 1971 | 7.139542838522 |
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