| Year | Value | | 2022 | 0.30335011590342 | | 2021 | 0.25785919973208 | | 2020 | 0.13454064739674 | | 2019 | 0.18842279049994 | | 2018 | 0.23303766036049 | | 2017 | 0.15566069119253 | | 2016 | 0.17121344196711 | | 2015 | 0.36181520045888 | | 2014 | 0.29516803148844 | | 2013 | 0.23029176498234 | | 2012 | 0.014227449516551 | | 2011 | 0.62077284342808 | | 2010 | 1.0951093891634 | | 2009 | 1.1133325436924 | | 2008 | 1.0999700107771 | | 2007 | 1.0810379997567 | | 2006 | 1.0185313836682 | | 2005 | 0.93364036238497 | | 2004 | 0.94243942173609 | | 2003 | 0.97472439182405 | | 2002 | 1.0222707708314 | | 2001 | 1.100300650511 | | 2000 | 1.1901891143893 | | 1999 | 1.2682537997018 | | 1998 | 1.2749285439923 | | 1997 | 1.1217601431042 | | 1996 | 0.73483092884532 | | 1995 | 0.50509409512558 | | 1994 | 0.54159394465084 | | 1993 | 0.57156384991499 | | 1992 | 0.76672491658542 | | 1991 | 1.305605158185 | | 1990 | 1.6471218979669 | | 1989 | 1.6431875342155 | | 1988 | 1.6370741579017 | | 1987 | 1.3685062711727 | | 1986 | 0.44482749128945 | | 1985 | 0.19243309578949 | | 1984 | 0.15182267552443 | | 1983 | 0.086652436332176 | | 1982 | 0.14859303727813 | | 1981 | 0.83372702563348 | | 1980 | 1.3365609283369 | | 1979 | 1.3370184429213 | | 1978 | 1.3356249549276 | | 1977 | 1.3174558634989 | | 1976 | 1.2465971627068 | | 1975 | 1.2927451538505 | | 1974 | 1.4535931321263 | | 1973 | 1.5655558900885 | | 1972 | 1.7356606112224 | | 1971 | 2.0281911385395 | | 1970 | 2.1921040115746 | | 1969 | 2.2223344477204 | | 1968 | 2.253514194499 | | 1967 | 1.9776337796204 | | 1966 | 1.3118521053273 | | 1965 | 0.92320080908813 | | 1964 | 0.9440147894851 | | 1963 | 0.94479230394683 | | 1962 | 0.5088021193731 | | 1961 | 0.76326040446332 |
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