Year | Value | 2021 | 40.054061735124 | 2020 | 40.023694871788 | 2019 | 39.908635953144 | 2018 | 39.905740347019 | 2017 | 39.918964875141 | 2016 | 39.866489465715 | 2015 | 39.873778164648 | 2014 | 39.846864511987 | 2013 | 39.926930424157 | 2012 | 39.977284741442 | 2011 | 39.990876079333 | 2010 | 39.996035105401 | 2009 | 39.956840571742 | 2008 | 40.007544450219 | 2007 | 40.257620421577 | 2006 | 40.203651201926 | 2005 | 40.165698713714 | 2004 | 40.628628681202 | 2003 | 40.663639333873 | 2002 | 40.640608219353 | 2001 | 40.580735091168 | 2000 | 40.472561207077 | 1999 | 40.522974869096 | 1998 | 40.22135769519 | 1997 | 39.887132969268 | 1996 | 39.605067080161 | 1995 | 39.351144407854 | 1994 | 39.060855344098 | 1993 | 38.792008084444 | 1992 | 39.123058822227 | 1991 | 38.251704650567 | 1990 | 38.224326151655 | 1989 | 37.937666291024 | 1988 | 37.672638110725 | 1987 | 37.457335764664 | 1986 | 37.069723805094 | 1985 | 36.839376732949 | 1984 | 36.546722883938 | 1983 | 36.248257911683 | 1982 | 36.220853204236 | 1981 | 36.144156059943 | 1980 | 36.251924149371 | 1979 | 36.258734862098 | 1978 | 36.159869258039 | 1977 | 36.084859134826 | 1976 | 36.025620209209 | 1975 | 36.005508725611 | 1974 | 35.99477185785 | 1973 | 35.970507875725 | 1972 | 35.904405854886 | 1971 | 35.76327946462 | 1970 | 35.744484551367 | 1969 | 35.725503365435 | 1968 | 35.789739498591 | 1967 | 35.781080923588 | 1966 | 35.790397662054 | 1965 | 35.792018234357 | 1964 | 35.810896970315 | 1963 | 35.843559884477 | 1962 | 35.893515112287 | 1961 | 35.905157154689 |
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