Year | Value | 2021 | 25.847792540492 | 2020 | 23.243161184963 | 2019 | 24.867345327002 | 2018 | 24.894894072721 | 2017 | 24.769287289235 | 2016 | 24.82835598847 | 2015 | 25.048692703114 | 2014 | 24.431934217603 | 2013 | 23.831391363238 | 2012 | 23.345765989474 | 2011 | 22.874670011683 | 2010 | 22.520603877613 | 2009 | 21.894874300616 | 2008 | 24.322809870073 | 2007 | 24.807237282434 | 2006 | 24.378085380834 | 2005 | 22.972111180598 | 2004 | 21.698596070751 | 2003 | 20.492767087035 | 2002 | 20.824892771236 | 2001 | 21.70059142643 | 2000 | 20.976063246416 | 1999 | 21.759931242672 | 1998 | 21.96394314318 | 1997 | 21.249839562528 | 1996 | 20.98463648179 | 1995 | 20.295526021468 | 1994 | 19.60437432227 | 1993 | 19.868835960902 | 1992 | 18.879989310963 | 1991 | 20.996142926019 | 1990 | 21.187451514287 | 1989 | 23.188835371125 | 1988 | 20.83862124981 | 1987 | 19.905876367337 | 1986 | 20.117171186865 | 1985 | 20.813175645104 | 1984 | 19.100369787632 | 1983 | 17.950009796512 | 1982 | 18.127921437454 | 1981 | 17.062846376883 | 1980 | 17.796573660554 | 1979 | 17.648831951771 | 1978 | 17.34111774668 | 1977 | 17.117414248021 | 1976 | 16.211608864545 | 1975 | 16.287425149701 | 1974 | 15.506880489279 | 1973 | 15.669540354373 | 1972 | 15.0270614454 |
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