Year | Value | 2022 | 15.411795679825 | 2021 | 16.089363900451 | 2020 | 15.472851187652 | 2019 | 15.638625530454 | 2018 | 14.544682153611 | 2017 | 16.402373961227 | 2016 | 18.580733899017 | 2015 | 15.206780873737 | 2014 | 13.237986853922 | 2013 | 14.549590317249 | 2012 | 12.819067778694 | 2011 | 17.550898809575 | 2010 | 17.146712477884 | 2009 | 17.676840765 | 2008 | 15.969012204646 | 2007 | 16.897279953249 | 2006 | 16.512084532374 | 2005 | 17.578546485927 | 2004 | 16.723379750213 | 2003 | 14.925677660121 | 2002 | 15.384578521789 | 2001 | 11.443953095056 | 2000 | 10.969746532017 | 1999 | 12.002885149592 | 1998 | 13.942940294968 | 1997 | 13.564332055007 | 1996 | 14.068930769463 | 1995 | 14.123004504139 | 1994 | 13.657314532445 | 1993 | 13.943834116857 | 1992 | 14.632789177198 | 1991 | 15.967060155536 | 1990 | 14.087797791722 | 1989 | 13.608413589158 | 1988 | 15.248031033641 | 1987 | 12.744814785391 | 1986 | 12.579303272843 | 1985 | 9.8320947956012 | 1984 | 10.014507775843 | 1983 | 10.925132415405 | 1982 | 14.89962479366 | 1981 | 16.981829548504 | 1980 | 8.0799478330658 | 1979 | 18.999706511987 | 1978 | 18.974994336643 |
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