| Year | Value | | 2022 | 7.9675736161788 | | 2021 | 4.1862150652357 | | 2020 | 1.6992846329935 | | 2019 | 0.67465277007806 | | 2018 | 0.92775542645691 | | 2017 | 0.98188986894312 | | 2016 | 1.2854484705142 | | 2015 | 2.5850039080159 | | 2014 | 0.19087507624975 | | 2013 | 1.8253947590917 | | 2012 | 2.5771817405584 | | 2011 | 3.5635147290396 | | 2010 | 1.4459451743086 | | 2009 | 3.7136059203581 | | 2008 | 8.6948281436391 | | 2007 | 0.94567327170517 | | 2006 | 2.2289777941404 | | 2005 | 6.7829289302831 | | 2004 | 0.39307868103157 | | 2003 | 0.93000088407215 | | 2002 | 3.0598185753587 | | 2001 | 3.9195913365316 | | 2000 | 1.8626059546307 | | 1999 | 0.05321362488249 | | 1998 | 0.97533838108874 | | 1997 | 8.250825082508 | | 1996 | 4.6875 | | 1995 | 16.433503452416 | | 1994 | 39.16276737968 | | 1993 | -1.0068816885504 | | 1992 | 1.3937866367594 | | 1991 | 0.38708179787073 | | 1990 | 1.0153415053081 | | 1989 | 0.83940311695255 | | 1988 | 0.15091097993478 | | 1987 | 0.054008850482671 | | 1986 | 4.1246152636769 | | 1985 | -1.8144143823216 | | 1984 | -3.5266287102055 | | 1983 | 9.3554650798615 | | 1982 | 11.129673328183 | | 1981 | 19.716502362481 | | 1980 | 12.30685721238 | | 1979 | 7.5392512077294 | | 1978 | 0.44277309395301 | | 1977 | 22.457013406618 | | 1976 | 11.640730810691 | | 1975 | 18.012199497668 | | 1974 | 12.83193169062 | | 1973 | 3.6153149657316 | | 1972 | 7.7266076782349 | | 1971 | 6.4920611363942 | | 1970 | 4.480620154651 | | 1969 | 6.0157790927021 | | 1968 | 0.29673590603654 | | 1967 | -2.3188405806762 |
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