| Year | Value | | 2022 | 1.5224769499459 | | 2021 | 1.3303716001551 | | 2020 | 1.5062677282985 | | 2019 | 0.50220335415772 | | 2018 | -2.4975417737835 | | 2017 | -3.7554844575692 | | 2016 | -1.151779789603 | | 2015 | 0.16945160522462 | | 2014 | 0.96108528030736 | | 2013 | 3.7094657324457 | | 2012 | 4.3794209950163 | | 2011 | 5.2988150209989 | | 2010 | 5.1235980252976 | | 2009 | 4.4912707147669 | | 2008 | 4.7111345458995 | | 2007 | 4.7226867045243 | | 2006 | 4.6765977770366 | | 2005 | 4.614186433986 | | 2004 | 4.5397409065682 | | 2003 | 4.4788381022268 | | 2002 | 4.4603289201929 | | 2001 | 4.4774268450979 | | 2000 | 4.4186739597559 | | 1999 | 2.6099224684906 | | 1998 | 1.9493486596966 | | 1997 | 2.8033718816392 | | 1996 | 2.4747987788611 | | 1995 | 3.0482101085463 | | 1994 | 2.4544204328011 | | 1993 | 1.2271258724674 | | 1992 | 1.8278724012308 | | 1991 | 2.4199137967798 | | 1990 | 0.93453001232153 | | 1989 | -2.27396119986 | | 1988 | -1.6260021746796 | | 1987 | 1.5266098339473 | | 1986 | 2.3659387372633 | | 1985 | 2.2328713631936 | | 1984 | 2.2074833455676 | | 1983 | 2.3424483530462 | | 1982 | 2.4029927913004 | | 1981 | 2.4006683025178 | | 1980 | 2.3953431861659 | | 1979 | 2.39557894824 | | 1978 | 2.4027378645904 | | 1977 | 2.3978603630201 | | 1976 | 2.4004679161761 | | 1975 | 2.4136273363324 | | 1974 | 2.4301840959151 | | 1973 | 2.2192434328852 | | 1972 | 1.9794211054933 | | 1971 | 1.6144063444053 | | 1970 | 1.2196466164818 | | 1969 | 1.2239440975884 | | 1968 | 1.2267257619377 | | 1967 | 1.1440893096971 | | 1966 | 1.3172407489534 | | 1965 | 1.7625024159055 | | 1964 | 1.7131365089472 | | 1963 | 1.4586952400213 | | 1962 | 1.4582104582334 | | 1961 | 1.407954752466 |
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