| Year | Value | | 2021 | 4.399600491278 | | 2020 | -4.8884954908669 | | 2019 | 2.855013146492 | | 2018 | 1.763122509322 | | 2017 | 2.2207996004515 | | 2016 | 5.2976221020257 | | 2015 | 5.8422780463423 | | 2014 | 3.6267342794982 | | 2013 | 2.4466468317499 | | 2012 | 6.2136993369967 | | 2011 | 3.587713454708 | | 2010 | 7.3487480177147 | | 2009 | 0.33741021665156 | | 2008 | 4.1433782508144 | | 2007 | 8.0356367723068 | | 2006 | 7.8084997675791 | | 2005 | 2.9468736316234 | | 2004 | 3.6766658571747 | | 2003 | 3.8731290141141 | | 2002 | 2.446056064897 | | 2001 | 3.6400413953521 | | 2000 | 2.0139825742864 | | 1999 | 0.31930984549065 | | 1998 | 7.1416798555303 | | 1997 | 7.4094816079607 | | 1996 | 0.25510161912993 | | 1995 | 3.8755380236579 | | 1994 | 7.5132727962613 | | 1993 | 7.9173160705045 | | 1992 | 10.668638534114 | | 1991 | 2.6993065665099 | | 1990 | 5.1776768838316 | | 1989 | 2.662204809501 | | 1988 | 2.2575573184542 | | 1987 | -1.8691391672667 | | 1986 | 12.578390703158 | | 1985 | 3.6281511873278 | | 1984 | 12.019906570384 | | 1983 | 10.844862721731 | | 1982 | -7.9403023226949 | | 1981 | -14.654146796284 | | 1980 | -1.009257317892 | | 1979 | 1.0476982288867 | | 1978 | 3.1451158879291 | | 1977 | 15.896203305285 | | 1976 | 9.9840863843669 | | 1975 | 6.1437802934796 | | 1974 | -1.664945960452 | | 1973 | 7.5267711986526 | | 1972 | 5.6099368539557 |
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