Year | Value | 2021 | 13.450445726272 | 2020 | 13.450445726272 | 2019 | 13.450445726272 | 2018 | 13.450445726272 | 2017 | 13.449035234899 | 2016 | 13.606333892617 | 2015 | 13.789122963507 | 2014 | 13.789122963507 | 2013 | 13.631712884015 | 2012 | 13.631712884015 | 2011 | 13.631712884015 | 2010 | 13.642206889314 | 2009 | 13.642206889314 | 2008 | 13.676312406538 | 2007 | 14.770312459008 | 2006 | 15.137602644489 | 2005 | 15.557362856468 | 2004 | 15.32124773723 | 2003 | 14.64824120603 | 2002 | 14.572864321608 | 2001 | 14.547738693467 | 2000 | 14.522613065327 | 1999 | 14.371859296482 | 1998 | 14.371859296482 | 1997 | 14.371859296482 | 1996 | 14.321608040201 | 1995 | 14.195979899497 | 1994 | 12.788944723618 | 1993 | 10.808381311132 | 1992 | 10.786978575862 | 1991 | 10.786978575862 | 1990 | 9.7168418123836 | 1989 | 9.6740363418445 | 1988 | 9.845258224001 | 1987 | 9.9522719003489 | 1986 | 9.502814459688 | 1985 | 9.502814459688 | 1984 | 9.502814459688 | 1983 | 9.203176165914 | 1982 | 8.9463433426792 | 1981 | 8.8393296663314 | 1980 | 8.8393296663314 | 1979 | 8.6681077841748 | 1978 | 8.561094107827 | 1977 | 8.561094107827 | 1976 | 8.5182886372878 | 1975 | 8.3898722256704 | 1974 | 8.3898722256704 | 1973 | 8.2400530787835 | 1972 | 8.2400530787835 | 1971 | 8.1758448729748 | 1970 | 8.1758448729748 | 1969 | 7.91901204974 | 1968 | 7.91901204974 | 1967 | 7.8762065792008 | 1966 | 7.8762065792008 | 1965 | 7.8334011086617 | 1964 | 7.8119983733921 | 1963 | 7.769192902853 | 1962 | 7.769192902853 | 1961 | 7.7263874323139 |
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