| Year | Value | | 2021 | 10.481948550045 | | 2020 | 10.403638688275 | | 2019 | 10.406890077197 | | 2018 | 10.429294555523 | | 2017 | 10.447499233527 | | 2016 | 10.458183952351 | | 2015 | 10.485145074895 | | 2014 | 10.510714079132 | | 2013 | 10.474053522243 | | 2012 | 10.49082754149 | | 2011 | 10.51383303463 | | 2010 | 10.429260909902 | | 2009 | 10.570800204858 | | 2008 | 10.552266519819 | | 2007 | 10.580629763215 | | 2006 | 10.743174328775 | | 2005 | 10.915935027824 | | 2004 | 10.991695732652 | | 2003 | 10.98587475884 | | 2002 | 11.108382949624 | | 2001 | 11.237104816598 | | 2000 | 11.298239703278 | | 1999 | 11.298218574862 | | 1998 | 11.315570479877 | | 1997 | 11.338663519822 | | 1996 | 11.334971914944 | | 1995 | 11.344863886618 | | 1994 | 11.43804551478 | | 1993 | 11.465247840057 | | 1992 | 11.408682987081 | | 1991 | 11.409388133408 | | 1990 | 11.415611809626 | | 1989 | 11.431760744548 | | 1988 | 11.436849710326 | | 1987 | 11.496282776218 | | 1986 | 11.554870682119 | | 1985 | 11.560024180231 | | 1984 | 11.573233597233 | | 1983 | 11.468472945501 | | 1982 | 11.484281672866 | | 1981 | 11.506611383999 | | 1980 | 11.489938113899 | | 1979 | 11.477485716494 | | 1978 | 11.446917316654 | | 1977 | 11.319017210396 | | 1976 | 11.293096631107 | | 1975 | 11.271383726612 | | 1974 | 11.316075151003 | | 1973 | 11.344644579484 | | 1972 | 11.429736278128 | | 1971 | 11.434899439012 | | 1970 | 11.55872988259 | | 1969 | 11.671494456722 | | 1968 | 11.468212937979 | | 1967 | 11.237228141289 | | 1966 | 11.279063996008 | | 1965 | 11.29218417789 | | 1964 | 11.302843001913 | | 1963 | 11.339383266854 | | 1962 | 11.256757530775 | | 1961 | 11.325815882657 |
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