Year | Value | 2023 | 15.782314031035 | 2022 | 15.445765448646 | 2021 | 7.4406112881633 | 2020 | 9.458804680866 | 2019 | 20.849245099568 | 2018 | 14.561088096547 | 2017 | 15.796490016148 | 2016 | 21.954215301665 | 2015 | 19.790623540493 | 2014 | 19.861470745036 | 2013 | 20.369158698705 | 2012 | 20.838214991978 | 2011 | 20.568653833741 | 2010 | 23.448358518824 | 2009 | 25.346324769885 | 2008 | 26.587454389132 | 2007 | 27.79379827732 | 2006 | 26.597064102879 | 2005 | 29.834357577113 | 2004 | 32.70077490616 | 2003 | 31.202276414332 | 2002 | 32.121539584919 | 2001 | 28.7439151798 | 2000 | 32.6849106107 | 1999 | 33.832850894146 | 1998 | 27.552456967579 | 1997 | 28.819587010214 | 1996 | 39.577877528401 | 1995 | 31.78619130942 | 1994 | 16.414851181344 | 1993 | 17.062419146184 | 1992 | 19.38887101962 | 1991 | 14.518378996902 | 1990 | 19.034112444725 | 1989 | 19.807642064011 | 1987 | 17.49078546392 | 1986 | 16.958543983822 | 1985 | 17.016418193494 | 1984 | 13.713193866053 | 1983 | 21.456602031394 | 1982 | 19.730089336628 | 1981 | 13.186119873817 | 1980 | 15.764247734591 | 1979 | 9.6157299863371 | 1978 | 9.6347909658818 | 1977 | 15.834502103787 |
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