| Year | Value | | 2022 | 0.3771020343901 | | 2021 | 0.52296324264195 | | 2020 | 0.53300660650007 | | 2019 | 0.56406554255668 | | 2018 | 0.54025108197947 | | 2017 | 0.48662526303083 | | 2016 | 0.44425716690466 | | 2015 | 0.39299524882491 | | 2014 | 0.39559288136206 | | 2013 | 0.44829630947071 | | 2012 | 0.49817016031484 | | 2011 | 0.58948960964437 | | 2010 | 0.60917975092629 | | 2009 | 0.6431061166878 | | 2008 | 0.70049222491123 | | 2007 | 0.73266596226376 | | 2006 | 0.68360213604724 | | 2005 | 0.60523748423895 | | 2004 | 0.59699223477319 | | 2003 | 0.67651024944203 | | 2002 | 0.90078308150976 | | 2001 | -1.1232086316798 | | 2000 | -1.1767862887923 | | 1999 | -1.070965688588 | | 1998 | 0.94804615743786 | | 1997 | 0.8364943249708 | | 1996 | 0.72139105416941 | | 1995 | -1.5211534415101 | | 1994 | -2.4488192163701 | | 1993 | -3.3338582444958 | | 1992 | -1.1978698848239 | | 1991 | 1.7031510753505 | | 1990 | 3.0939585306458 | | 1989 | 2.3874270688744 | | 1988 | 0.46065978260669 | | 1987 | 0.72417276696235 | | 1986 | 0.79317527072335 | | 1985 | 0.87613549216354 | | 1984 | 1.0386870341093 | | 1983 | 1.1266671586127 | | 1982 | 1.0717718149534 | | 1981 | 1.0392924006999 | | 1980 | 1.2215779148193 | | 1979 | 1.9179494442449 | | 1978 | 2.4219726048738 | | 1977 | 2.3615549865221 | | 1976 | 2.2879207555209 | | 1975 | 2.2561511301816 | | 1974 | 2.2210803335649 | | 1973 | 2.1963571269029 | | 1972 | 2.1808581915812 | | 1971 | 2.2066335412349 | | 1970 | 2.3158511236035 | | 1969 | 2.4485263105799 | | 1968 | 2.5340080684816 | | 1967 | 2.6015050278008 | | 1966 | 2.7132412773172 | | 1965 | 2.8615280686174 | | 1964 | 3.0343410867038 | | 1963 | 3.2228669618049 | | 1962 | 3.3819277161697 | | 1961 | 3.4775226619034 |
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