Year | Value | 2022 | 17.856389010252 | 2021 | 19.66675985899 | 2020 | 19.878156559545 | 2019 | 20.713016507222 | 2018 | 20.400871735452 | 2017 | 20.590616259376 | 2016 | 20.374234479676 | 2015 | 20.62819524947 | 2014 | 21.21149717869 | 2013 | 22.479795896284 | 2012 | 22.865868467304 | 2011 | 23.700102854868 | 2010 | 22.446143370597 | 2009 | 20.920441917375 | 2008 | 22.751176865831 | 2007 | 24.116418475221 | 2006 | 23.326656365598 | 2005 | 19.742073426791 | 2004 | 17.837255694834 | 2003 | 16.80110880287 | 2002 | 16.951753375854 | 2001 | 16.664797509325 | 2000 | 17.319379461169 | 1999 | 18.396232533546 | 1998 | 17.751426085809 | 1997 | 18.256757980132 | 1996 | 16.258470423888 | 1995 | 16.389276069664 | 1994 | 16.765480608724 | 1993 | 13.349475595029 | 1992 | 13.090892305614 | 1991 | 13.957281203546 | 1990 | 13.054045869749 | 1989 | 17.045878639358 | 1988 | 14.897443804702 | 1987 | 15.309599954657 | 1986 | 14.80591995818 | 1985 | 24.337461861311 | 1984 | 22.279531587856 | 1983 | 22.22215363092 | 1982 | 27.104449956756 | 1981 | 24.668008047507 | 1980 | 28.650118915803 | 1979 | 26.592788594829 | 1978 | 18.01871027201 | 1977 | 12.292656304479 |
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