| Year | Value | | 2021 | 7.058612208467 | | 2020 | -3.9343562788777 | | 2019 | 0.58373498819613 | | 2018 | 0.56679766162853 | | 2017 | 3.9995218696726 | | 2016 | 5.3132139239749 | | 2015 | -3.2759693913001 | | 2014 | -1.8114816378629 | | 2013 | 0.46927881545953 | | 2012 | 10.34607933383 | | 2011 | 3.4489261001661 | | 2010 | 16.211796848951 | | 2009 | -2.9606611742446 | | 2008 | 6.8958488296023 | | 2007 | 8.9555661595167 | | 2006 | 10.112549783451 | | 2005 | 10.719549198393 | | 2004 | 5.2022794548453 | | 2003 | 9.4725082354105 | | 2002 | 3.6911694388269 | | 2001 | 6.1345178561726 | | 2000 | 19.35077683128 | | 1999 | 0.6858246977894 | | 1998 | 3.2790356758611 | | 1997 | 3.1923515491793 | | 1996 | 1.422135230113 | | 1995 | 0.42684588950316 | | 1994 | 0.29009579440486 | | 1993 | -7.32522871577 | | 1992 | 0.063968849149347 | | 1991 | -1.0606430845446 | | 1990 | 0.27040166126949 | | 1989 | 3.5787208481515 | | 1988 | -4.4280962640038 | | 1987 | -11.392126380516 | | 1986 | -8.8038240837508 | | 1985 | 4.2471493962722 | | 1984 | 2.2024100508754 | | 1983 | 6.7143254718767 | | 1982 | 5.8127526076711 | | 1981 | 17.302581091022 | | 1980 | 30.717483990234 | | 1979 | -8.1072277270838 | | 1978 | 10.835696508236 | | 1977 | 5.4172285479537 | | 1976 | 5.0355551313594 | | 1975 | 1.4180472635599 | | 1974 | 12.60320203609 | | 1973 | -2.9518543896598 | | 1972 | 10.708088395328 | | 1971 | 4.3685565770236 |
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