| Year | Value | | 2021 | 4.8925450710243 | | 2020 | -11.941753299587 | | 2019 | 5.0329978296282 | | 2018 | 6.1003790237735 | | 2017 | 2.5928706413825 | | 2016 | 7.2932333879245 | | 2015 | 11.268033374514 | | 2014 | 6.8866385683621 | | 2013 | 2.6455749499121 | | 2012 | 2.8926538238185 | | 2011 | 1.0902249141718 | | 2010 | 7.0804212033259 | | 2009 | 4.0153788313792 | | 2008 | 4.6569928485946 | | 2007 | 6.474655355752 | | 2006 | 8.5710965383721 | | 2005 | 11.429579224386 | | 2004 | 0.62644385860121 | | 2003 | -6.4791105692302 | | 2002 | 3.307034300576 | | 2001 | 4.1333139694294 | | 2000 | 2.877884994291 | | 1999 | 3.9462319407479 | | 1998 | 9.5060775934714 | | 1997 | 10.754896309353 | | 1996 | 6.8676218588302 | | 1995 | 5.5754985354413 | | 1994 | 4.8483954790307 | | 1993 | 5.5392006464177 | | 1992 | 11.842145102246 | | 1991 | 7.7445654789137 | | 1990 | -7.2878104338136 | | 1989 | 3.1148682458152 | | 1988 | 7.4020790076804 | | 1987 | 6.4053710398928 | | 1986 | 11.616801660771 | | 1985 | 11.049112538111 | | 1984 | -5.6155165276174 | | 1983 | 1.1867830146714 | | 1982 | 1.9959222120727 | | 1981 | 2.1796438793052 | | 1980 | 5.2520310263367 | | 1979 | 1.686658961822 | | 1978 | 0.75060220337903 | | 1977 | 4.3230747131015 | | 1976 | -2.0361984539478 | | 1975 | 11.630427984335 | | 1974 | 5.1802404702652 | | 1973 | 9.4500213951212 | | 1972 | 13.984430051963 |
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