| Year | Value | | 2022 | -1.8569124928959 | | 2021 | -1.249035166917 | | 2020 | -2.0793369059084 | | 2019 | -2.8798658955212 | | 2018 | -2.6272125410546 | | 2017 | -2.4155210315248 | | 2016 | -2.2172797902348 | | 2015 | 1.9663732686465 | | 2014 | 9.9719695424286 | | 2013 | 9.2264961282358 | | 2012 | 2.6075208412108 | | 2011 | 0.98111944066669 | | 2010 | 0.89807162101219 | | 2009 | 1.2912797977466 | | 2008 | 1.6088461333698 | | 2007 | 1.8835598292098 | | 2006 | 1.6409799998653 | | 2005 | 1.4807859466033 | | 2004 | 1.5417277303209 | | 2003 | 1.2990446960809 | | 2002 | 1.3007623759812 | | 2001 | 1.5742975808914 | | 2000 | 1.6480313517987 | | 1999 | 1.6903393684108 | | 1998 | 1.7193307959669 | | 1997 | 1.800831146885 | | 1996 | 1.8665563651982 | | 1995 | 1.8221189093623 | | 1994 | 1.7996733257644 | | 1993 | 1.9404900389951 | | 1992 | 2.1228941703766 | | 1991 | 2.0119035174757 | | 1990 | 1.9159474951042 | | 1989 | 1.957886576269 | | 1988 | 1.9357446074711 | | 1987 | 2.4739725503333 | | 1986 | 2.4871361398323 | | 1985 | 1.9778095172829 | | 1984 | 1.8042931693384 | | 1983 | 1.1933528730663 | | 1982 | 1.407551584541 | | 1981 | 2.1206204722566 | | 1980 | 2.098249695327 | | 1979 | -9.249471304508 | | 1978 | -8.2628244803508 | | 1977 | 11.876558909266 | | 1976 | 13.168342341968 | | 1975 | 2.2052306864989 | | 1974 | 2.423427479733 | | 1973 | 2.5170139393065 | | 1972 | 2.5800414224916 | | 1971 | 2.5020749981161 | | 1970 | 2.4639051390629 | | 1969 | 2.6835657664752 | | 1968 | 2.6466259872083 | | 1967 | 2.6471084222437 | | 1966 | 2.7499842449532 | | 1965 | 2.768831175484 | | 1964 | 2.945226450758 | | 1963 | 3.0671882943319 | | 1962 | 3.1163234957411 | | 1961 | 3.023903322244 |
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