Year | Value | 2021 | 28.986842105263 | 2020 | 28.986842105263 | 2019 | 28.986842105263 | 2018 | 28.986842105263 | 2017 | 28.686699857753 | 2016 | 28.386557610242 | 2015 | 28.086415362731 | 2014 | 27.78613086771 | 2013 | 27.485846372688 | 2012 | 27.185561877667 | 2011 | 26.885277382646 | 2010 | 26.584992887625 | 2009 | 26.284672830726 | 2008 | 25.984352773827 | 2007 | 25.684032716928 | 2006 | 25.383712660029 | 2005 | 25.083392603129 | 2004 | 24.78307254623 | 2003 | 24.482752489331 | 2002 | 24.182432432432 | 2001 | 23.882112375533 | 2000 | 23.581792318634 | 1999 | 23.281472261735 | 1998 | 22.981152204836 | 1997 | 22.680832147937 | 1996 | 22.380512091038 | 1995 | 22.080192034139 | 1994 | 21.77987197724 | 1993 | 21.424253200569 | 1992 | 20.713015647226 | 1991 | 20.713015647226 | 1990 | 20.578591749644 | 1989 | 20.222972972973 | 1988 | 18.907183499289 | 1987 | 19.26280227596 | 1986 | 19.440611664296 | 1985 | 20.614153627311 | 1984 | 20.329658605974 | 1983 | 19.369487908962 | 1982 | 19.01386913229 | 1981 | 18.551564722617 | 1980 | 18.302631578947 | 1979 | 18.195945945946 | 1978 | 18.160384068279 | 1977 | 18.160384068279 | 1976 | 18.124822190612 | 1975 | 18.124822190612 | 1974 | 18.124822190612 | 1973 | 17.947012802276 | 1972 | 17.76920341394 | 1971 | 17.76920341394 | 1970 | 17.76920341394 | 1969 | 17.76920341394 | 1968 | 17.76920341394 | 1967 | 17.76920341394 | 1966 | 17.413584637269 | 1965 | 17.413584637269 | 1964 | 17.413584637269 | 1963 | 17.413584637269 | 1962 | 17.413584637269 | 1961 | 17.413584637269 |
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