| Year | Value | | 2022 | 4.510301492357 | | 2021 | 2.8683302775102 | | 2020 | 1.4470365699874 | | 2019 | -2.162178834706 | | 2018 | 13.170203853672 | | 2017 | 25.803618478834 | | 2016 | 25.853874212446 | | 2015 | 10.402293358815 | | 2014 | 2.4329414159923 | | 2013 | 2.6058180271952 | | 2012 | 6.0598039215686 | | 2011 | 15.518481531756 | | 2010 | 2.7998950010927 | | 2009 | 2.4599002560995 | | 2008 | 10.3607288955 | | 2007 | 6.2509878299355 | | 2006 | 1.4592687620272 | | 2005 | 2.6502057613166 | | 2004 | -2.197567740559 | | 2003 | -2.1911519198664 | | 2002 | -9.7976470588236 | | 2001 | -8.8139375214555 | | 2000 | -2.9000000000002 | | 1999 | 2.6486225229582 | | 1998 | 3.7092731829574 | | 1997 | 3.5502958579882 | | 1996 | 4.0280777537796 | | 1995 | 7.2379849449913 | | 1994 | 5.1125989044431 | | 1993 | 11.073553272039 | | 1992 | 9.3597515895313 | | 1991 | 11.896095301125 | | 1990 | 8.4514624080388 | | 1989 | 1.5118397085609 | | 1988 | 6.0869565217391 | | 1987 | 4.3557168784029 | | 1986 | 3.2909810456156 | | 1985 | 9.1384405546716 | | 1984 | 12.477627205318 | | 1983 | 10.60520361991 | | 1982 | 10.258808855628 | | 1981 | 11.199722607489 | | 1980 | 9.7342887947139 | | 1979 | -6.0390287501709 | | 1978 | 29.37979416417 | | 1977 | 6.2802130275091 | | 1976 | 5.4792152796885 | | 1975 | 9.1192003014564 | | 1974 | 7.4584515608289 | | 1973 | 7.970895563186 | | 1972 | 0.25102319208901 | | 1971 | -3.1038494081085 | | 1970 | -5.296371422047 | | 1969 | 9.7859705554738 | | 1968 | 0.39123144730921 | | 1967 | 7.2961087423089 | | 1966 | 12.242913768341 | | 1965 | 11.424999999668 |
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