| Year | Value | | 2023 | 0.047801854432771 | | 2022 | 0.39325087381394 | | 2021 | 0.74603647852306 | | 2020 | 0.55075989254178 | | 2019 | 0.52681482193634 | | 2018 | 0.58749330740358 | | 2017 | 0.57800701514689 | | 2016 | 0.57366084537962 | | 2015 | 0.47005222786465 | | 2014 | 0.37457549776226 | | 2013 | 0.37132306287804 | | 2012 | 0.44517793619838 | | 2011 | 0.49186621286604 | | 2010 | 0.59395918358863 | | 2009 | 0.83308875477898 | | 2008 | -1.6663826430655 | | 2007 | -1.4772229819772 | | 2006 | 0.59240256002911 | | 2005 | 0.61753095660306 | | 2004 | 0.56978627253288 | | 2003 | 0.7212622974018 | | 2002 | -1.8306549937016 | | 2001 | -1.3954299863575 | | 2000 | 0.12944003980625 | | 1999 | 0.15697861602444 | | 1998 | 0.20698024194077 | | 1997 | 0.28789795154156 | | 1996 | 0.2881294855309 | | 1995 | 0.20231879638046 | | 1994 | 0.14537906455364 | | 1993 | 0.13610914221148 | | 1992 | 0.9034629284532 | | 1991 | 0.86869383124165 | | 1990 | 0.17417662808295 | | 1989 | 0.44914820746576 | | 1988 | 0.4705022419719 | | 1987 | 0.49180343571986 | | 1986 | 0.45574959113216 | | 1985 | 0.4075155507793 | | 1984 | 0.35427994718411 | | 1983 | 0.37630645678429 | | 1982 | 0.54728779753132 | | 1981 | 0.65434186954 | | 1980 | 0.52731444779974 | | 1979 | 0.63132742963497 | | 1978 | 0.8939840208936 | | 1977 | 0.94423567856391 | | 1976 | 1.2045877621637 | | 1975 | 1.2482922061614 | | 1974 | 0.92558879324995 |
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