| Year | Value | | 2022 | 10.001207875347 | | 2021 | 2.6757200880539 | | 2020 | 1.2724603778916 | | 2019 | 2.633699102496 | | 2018 | 1.7034979474447 | | 2017 | 1.3814587140721 | | 2016 | 0.31666666666674 | | 2015 | 0.60024814727878 | | 2014 | 0.97603507969968 | | 2013 | 2.5068985265788 | | 2012 | 2.455547652916 | | 2011 | 2.3410701775137 | | 2010 | 1.2753056955668 | | 2009 | 1.1897768702155 | | 2008 | 2.4865019828945 | | 2007 | 1.613858598021 | | 2006 | 1.101501065177 | | 2005 | 1.6881301786962 | | 2004 | 1.2636473918318 | | 2003 | 2.0919983899765 | | 2002 | 3.2875310471277 | | 2001 | 4.1558412719561 | | 2000 | 2.3605223380195 | | 1999 | 2.1571791805506 | | 1998 | 1.9591363227425 | | 1997 | 2.1092456273948 | | 1996 | 1.9493671316601 | | 1995 | 1.9232200345352 | | 1994 | 2.8015246329318 | | 1993 | 2.584184486718 | | 1992 | 3.1835818176155 | | 1991 | 3.1582004147712 | | 1990 | 2.4540918481834 | | 1989 | 1.082158102533 | | 1988 | 0.73795068833232 | | 1987 | 0.69121048141152 | | 1986 | 0.083346777108539 | | 1985 | 2.2585844298862 | | 1984 | 3.301640757593 | | 1983 | 2.7408403316226 | | 1982 | 5.9110965846838 | | 1981 | 6.7389265520478 | | 1980 | 6.513455455218 | | 1979 | 4.1992999016835 | | 1978 | 4.1120119626929 | | 1977 | 6.399294874061 | | 1976 | 8.8306515860316 | | 1975 | 10.217475794824 | | 1974 | 9.5914226726851 | | 1973 | 8.0222099587894 | | 1972 | 7.8027921925661 | | 1971 | 7.4776786767116 | | 1970 | 3.6689308880866 | | 1969 | 7.4217900550128 | | 1968 | 3.7207932801914 | | 1967 | 3.4553321831471 | | 1966 | 5.7621402362246 | | 1965 | 3.9080378277962 | | 1964 | 5.8237682581744 | | 1963 | 3.243647373964 | | 1962 | 2.4311226441781 | | 1961 | 1.3076393668273 | | 1960 | 2.3239436619722 |
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