| Year | Value | | 2022 | 0.252206943271 | | 2021 | 0.77341275828697 | | 2020 | 0.50157764464777 | | 2019 | 0.064389617935735 | | 2018 | 0.29320375195086 | | 2017 | 0.6540014472751 | | 2016 | 0.78334030611565 | | 2015 | 0.54063065714161 | | 2014 | 0.31196593678607 | | 2013 | 0.46072623166492 | | 2012 | 1.9413351389705 | | 2011 | 2.7675978237222 | | 2010 | 1.7521631657004 | | 2009 | 1.1625966858934 | | 2008 | 1.0741523242164 | | 2007 | 1.3691351096137 | | 2006 | 1.5168367232794 | | 2005 | 1.4163817609538 | | 2004 | 1.7055913163008 | | 2003 | 2.2344928266843 | | 2002 | 2.2928821635704 | | 2001 | 1.8908203925672 | | 2000 | 1.5744214594766 | | 1999 | 1.5534367077744 | | 1998 | 1.5545057471567 | | 1997 | 1.4204169484988 | | 1996 | 1.3926523438786 | | 1995 | 1.4204726811573 | | 1994 | 1.4533468717407 | | 1993 | 1.5545542173778 | | 1992 | 1.4767442079805 | | 1991 | 1.4037276274904 | | 1990 | 1.4324834043959 | | 1989 | 1.1511870432126 | | 1988 | 0.46688539422467 | | 1987 | 0.20969512669767 | | 1986 | 0.66769982103564 | | 1985 | 0.65408357333707 | | 1984 | 0.55821697518067 | | 1983 | 0.77209877130954 | | 1982 | 0.95853268459938 | | 1981 | 1.1643743864267 | | 1980 | 1.2207631629895 | | 1979 | 1.3944163667003 | | 1978 | 1.5166121541629 | | 1977 | 1.5846008450078 | | 1976 | 1.7867001828424 | | 1975 | 1.8552083994768 | | 1974 | 2.2316200879638 | | 1973 | 2.3148565896515 | | 1972 | 1.9735873131287 | | 1971 | 0.23638723522321 | | 1970 | -1.2796849682754 | | 1969 | 0.61045592092687 | | 1968 | 2.1217437739166 | | 1967 | 1.7974846536059 | | 1966 | 1.8072262607416 | | 1965 | 2.0293687463233 | | 1964 | 2.0472827015953 | | 1963 | 2.0777594371743 | | 1962 | 2.1595885497453 | | 1961 | 2.1558178069265 |
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