| Year | Value | | 2021 | 8.8804301127496 | | 2020 | -7.3945619568119 | | 2019 | 1.8851344025976 | | 2018 | 2.3284503516103 | | 2017 | 5.1176907363751 | | 2016 | 0.63080775317017 | | 2015 | -2.3319027009357 | | 2014 | 2.190365176689 | | 2013 | 2.6793281961924 | | 2012 | 1.4095868911988 | | 2011 | 4.5405956964692 | | 2010 | 5.5509714764715 | | 2009 | -6.1627773242171 | | 2008 | 1.3104905099551 | | 2007 | 2.9900567246972 | | 2006 | 4.820190271826 | | 2005 | 3.7849117315315 | | 2004 | 5.6070372938429 | | 2003 | 3.1606761767655 | | 2002 | 2.9947700877616 | | 2001 | 1.0985781031589 | | 2000 | 6.8283373386213 | | 1999 | 5.9953574716928 | | 1998 | 2.0261569266812 | | 1997 | 4.2583500258092 | | 1996 | 1.5200464749168 | | 1995 | 4.0313711432055 | | 1994 | 4.340050080728 | | 1993 | 2.4914777610344 | | 1992 | 0.23731351078762 | | 1991 | -1.7611652612485 | | 1990 | 0.88519436728404 | | 1989 | 2.4824800634969 | | 1988 | 4.6536445920793 | | 1987 | 5.1861230659211 | | 1986 | 2.057512509275 | | 1985 | 4.7701042356275 | | 1984 | 5.5470732084589 | | 1983 | 3.3713401386488 | | 1982 | -2.8294417508341 | | 1981 | 3.1883922075993 | | 1980 | 1.6064408216437 | | 1979 | 1.0704805409577 | | 1978 | 2.7363171311448 | | 1977 | 2.0662268330719 | | 1976 | 5.5720543178661 | | 1975 | 2.5303674834155 | | 1974 | 3.7334298148012 | | 1973 | 7.3492837099139 | | 1972 | 6.5396215593065 | | 1971 | 4.9891470500879 |
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