| Year | Value | | 2021 | 2.8721731240409 | | 2020 | -5.4385780067054 | | 2019 | 0.47128214159531 | | 2018 | -2.7753573450157 | | 2017 | 2.1379826353461 | | 2016 | -1.8364632954557 | | 2015 | 1.5037130098812 | | 2014 | 4.0593207717091 | | 2013 | 7.4745438038662 | | 2012 | 7.1026528015528 | | 2011 | 5.7318451727361 | | 2010 | 1.1629619736925 | | 2009 | 7.2362405918169 | | 2008 | 9.4751951545598 | | 2007 | 6.0444555460532 | | 2006 | 4.854539171553 | | 2005 | 2.6664795238817 | | 2004 | 1.8877591253881 | | 2003 | 2.3087662884414 | | 2002 | 9.0833845974402 | | 2001 | 12.088821050424 | | 2000 | -3.7606856476302 | | 1999 | -12.562039437642 | | 1998 | 3.1244178955429 | | 1997 | 8.0712881414209 | | 1996 | 0.93259486067834 | | 1995 | 0.55919255752705 | | 1994 | 4.441170509561 | | 1993 | -6.1748653526177 | | 1992 | 5.4546436603484 | | 1991 | 14.052368201654 | | 1990 | 8.266551129757 | | 1989 | -1.7134070973128 | | 1988 | -7.3323890931993 | | 1987 | -1.4292228463205 | | 1986 | 0.4122929515382 | | 1985 | 7.2063333437306 | | 1984 | 1.2670407227104 | | 1983 | -7.4388769017097 | | 1982 | 0.47172918471577 | | 1981 | 7.5174743834772 | | 1980 | 5.1724154662164 | | 1979 | -1.1292853249476 | | 1978 | 1.6293465239868 | | 1977 | 6.7064997590026 | | 1976 | 6.7993148721149 | | 1975 | 14.283763826412 | | 1974 | 15.950562518214 | | 1973 | 3.5809698791226 | | 1972 | 0.47811469082147 | | 1971 | 5.6227171110942 |
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