| Year | Value | | 2022 | 2.8574828218533 | | 2021 | 1.6307033730189 | | 2020 | -1.5502754080376 | | 2019 | 0.35508382102126 | | 2018 | 0.76157835940001 | | 2017 | 0.87558591875985 | | 2016 | 0.73973402530004 | | 2015 | 0.13639971040352 | | 2014 | 2.6266836535332 | | 2013 | 4.0271605344298 | | 2012 | 5.6981994030787 | | 2011 | 5.8758024998975 | | 2010 | 3.4912886748753 | | 2009 | 2.4090531666971 | | 2008 | 8.7586830879568 | | 2007 | 4.1686331647715 | | 2006 | 2.4578933314339 | | 2005 | 3.1817051951281 | | 2004 | 0.1826180791898 | | 2003 | 0.39166666666669 | | 2002 | 1.0058309037904 | | 2001 | 0.30706243602871 | | 2000 | 1.4989611160578 | | 1999 | 1.2471825694964 | | 1998 | 0.55908129344248 | | 1997 | 1.3243512210061 | | 1996 | 1.2557166111155 | | 1995 | 0.99420698293385 | | 1994 | 1.268431901062 | | 1993 | 0.45393007884038 | | 1992 | 1.8245215698996 | | 1991 | 1.2562607767469 | | 1990 | 0.76948535495602 | | 1989 | 0.20586725831773 | | 1988 | 0.35922084492819 | | 1987 | 0.99642309667918 | | 1986 | 0.066384108359381 | | 1985 | 1.0266198927516 | | 1984 | 1.5826433285859 | | 1983 | 2.1028412436817 | | 1982 | 4.2505717632812 | | 1981 | 7.3023283652622 | | 1980 | 13.807901907801 | | 1979 | 7.9888185961077 | | 1978 | 4.200521232661 | | 1977 | 4.5855379188961 | | 1976 | 3.9499999994172 | | 1975 | 5.8810413065095 | | 1974 | 16.268066627712 | | 1973 | 6.8564305005337 | | 1972 | 5.4095488394893 | | 1971 | 1.9196428571514 | | 1970 | 3.0832949836703 | | 1969 | 1.8275538894136 | | 1968 | 1.6190476195355 | | 1967 | 1.3758146270918 | | 1966 | 0.19347037509254 | | 1965 | 0.46161321671988 | | 1964 | 2.4135357049138 | | 1963 | 0.44988752811995 | | 1962 | 0.78800203355598 | | 1961 | 0.61381074194671 | | 1960 | 0.051177072415786 |
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