| Year | Value | | 2022 | 0.83148347874786 | | 2021 | 0.928803634266 | | 2020 | 1.0275734267733 | | 2019 | 0.97384038407045 | | 2018 | 0.96115615274954 | | 2017 | 0.89266323121925 | | 2016 | 0.95095330162857 | | 2015 | 1.0674493490885 | | 2014 | 0.98660539173451 | | 2013 | 0.96416726024498 | | 2012 | 0.96450678803369 | | 2011 | 0.84460385084958 | | 2010 | 0.75054485877204 | | 2009 | 0.75348371210512 | | 2008 | 0.68312427518439 | | 2007 | 0.74143684839604 | | 2006 | 0.79345513493382 | | 2005 | 0.72148039978203 | | 2004 | 0.8776300638874 | | 2003 | 0.82575537178434 | | 2002 | 0.97123693298858 | | 2001 | 1.0746348172333 | | 2000 | 1.2449394538465 | | 1999 | 1.388767852038 | | 1998 | 1.5431537152831 | | 1997 | 1.6856803065861 | | 1996 | 2.0637899367078 | | 1995 | 2.2834245690128 | | 1994 | 2.0467663709092 | | 1993 | 2.1785476648296 | | 1992 | 2.3688899773908 | | 1991 | 2.8293270046069 | | 1990 | 2.131875856253 | | 1989 | 2.4257637557947 | | 1988 | 3.1954734453196 | | 1987 | 2.7731923325715 | | 1986 | 3.8040656378529 | | 1985 | 3.7576348428929 | | 1984 | 3.5081851768898 | | 1983 | 3.6452417986962 | | 1982 | 3.8032975754999 | | 1981 | 2.5278601828607 | | 1980 | 2.1814492214301 | | 1979 | 2.0263982623929 | | 1978 | 2.9585323183129 | | 1977 | 2.8886446553484 | | 1976 | 2.9899565069553 | | 1975 | 3.1250035643609 | | 1974 | 2.5645724201788 | | 1973 | 3.4174372291334 | | 1972 | 3.8464631330798 | | 1971 | 3.2252254697209 | | 1970 | 3.3158722914382 | | 1969 | 3.1614860487958 | | 1968 | 3.2110495873666 | | 1967 | 3.0315589946833 | | 1966 | 2.9168450601609 | | 1965 | 2.6330876800904 | | 1964 | 2.4037657614708 | | 1963 | 2.3988542198956 | | 1962 | 2.2973921137169 | | 1961 | 2.2791496811027 | | 1960 | 2.5289644657641 |
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