Year | Value | 2021 | 29.78912978913 | 2020 | 29.843480843481 | 2019 | 30.0297000297 | 2018 | 30.32373032373 | 2017 | 30.798930798931 | 2016 | 30.531630531631 | 2015 | 30.947430947431 | 2014 | 31.018106262986 | 2013 | 30.822202433957 | 2012 | 29.982206405694 | 2011 | 29.833926453144 | 2010 | 30.317225022235 | 2009 | 31.268900088942 | 2008 | 31.593601895735 | 2007 | 31.392180094787 | 2006 | 31.688388625592 | 2005 | 32.908767772512 | 2004 | 33.397511848341 | 2003 | 32.319312796209 | 2002 | 30.071090047393 | 2001 | 29.881516587678 | 2000 | 30.293246445498 | 1999 | 29.958530805687 | 1998 | 27.544431279621 | 1997 | 28.767772511848 | 1996 | 27.461492890995 | 1995 | 27.221563981043 | 1994 | 26.756516587678 | 1993 | 26.726895734597 | 1992 | 26.664691943128 | 1991 | 26.430687203791 | 1990 | 27.381516587678 | 1989 | 26.851303317535 | 1988 | 26.771327014218 | 1987 | 26.466232227488 | 1986 | 26.007109004739 | 1985 | 25.512440758294 | 1984 | 24.934834123223 | 1983 | 24.700829383886 | 1982 | 25.245853080569 | 1981 | 25.053317535545 | 1980 | 25.041469194313 | 1979 | 24.617890995261 | 1978 | 24.517180094787 | 1977 | 24.715639810426 | 1976 | 24.108412322275 | 1975 | 23.97808056872 | 1974 | 23.886255924171 | 1973 | 23.797393364929 | 1972 | 23.995853080569 | 1971 | 24.167654028436 | 1970 | 24.650473933649 | 1969 | 25.266587677725 | 1968 | 25.826421800948 | 1967 | 26.116706161137 | 1966 | 26.86018957346 | 1965 | 27.488151658768 | 1964 | 27.754739336493 | 1963 | 28.11018957346 | 1962 | 28.613744075829 | 1961 | 29.383886255924 |
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