Year | Value | 2021 | 16.991788691603 | 2020 | 13.062631293168 | 2019 | 25.014981617011 | 2018 | 22.92840096799 | 2017 | 20.444273572563 | 2016 | 21.304227524469 | 2015 | 24.169642682567 | 2014 | 24.97471085486 | 2013 | 24.192634952874 | 2012 | 23.306871479579 | 2011 | 22.180229197973 | 2010 | 24.288597609868 | 2009 | 16.470376643512 | 2008 | 21.688171160124 | 2007 | 18.639940892392 | 2006 | 20.665582888154 | 2005 | 20.212800378328 | 2004 | 12.965343486323 | 2003 | 14.007111212985 | 2002 | 14.593412747415 | 2001 | 15.254855507916 | 2000 | 13.448202135311 | 1999 | 10.560268331894 | 1998 | 13.443612669352 | 1997 | 11.535548900129 | 1996 | 13.553576241743 | 1995 | 8.5102078470791 | 1994 | 9.5360050169142 | 1993 | 5.4508832179799 | 1992 | 6.0986747989443 | 1991 | 8.2462594704512 | 1990 | 6.8818184977827 | 1989 | 6.8201579990347 | 1988 | 13.314790859652 | 1987 | 4.3632800438694 | 1986 | 9.9152416737323 | 1985 | 8.3212877434107 | 1984 | 2.3877112349557 | 1983 | 9.000756060377 | 1982 | 6.7101805701427 | 1981 | 10.056995415569 | 1980 | 17.124536497616 | 1979 | 19.116572536483 | 1978 | 20.729753047179 | 1977 | 14.021795258251 | 1976 | 10.313487592626 | 1975 | 7.7470647827126 | 1974 | 5.3998407374954 |
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