Year | Value | 2022 | 24.082933875674 | 2021 | 23.265564342503 | 2020 | 19.472297156359 | 2019 | 20.261633986119 | 2018 | 19.582931230402 | 2017 | 19.845280989292 | 2016 | 19.146454571981 | 2015 | 19.569363631568 | 2014 | 22.148493894754 | 2013 | 21.597298402506 | 2012 | 20.917951228194 | 2011 | 20.857109411382 | 2010 | 19.312530097616 | 2009 | 18.520013474572 | 2008 | 24.247409305481 | 2007 | 24.404319557488 | 2006 | 24.617277079787 | 2005 | 24.451754139057 | 2004 | 23.660504071832 | 2003 | 21.943777150402 | 2002 | 21.724737198022 | 2001 | 22.635489053482 | 2000 | 23.774628073122 | 1999 | 21.095886781962 | 1998 | 19.774214276071 | 1997 | 20.196734015002 | 1996 | 19.461567580578 | 1995 | 18.949594812256 | 1994 | 16.982990179113 | 1993 | 14.883827947969 | 1992 | 14.056917651052 | 1991 | 15.142207882611 | 1990 | 17.759890764973 | 1989 | 20.138475622311 | 1988 | 20.96099337985 | 1987 | 20.166792347543 | 1986 | 18.967020544479 | 1985 | 20.534191947883 | 1984 | 20.912067028604 | 1983 | 20.052433363505 | 1982 | 19.900019725663 | 1981 | 22.4920879562 | 1980 | 22.170476495759 | 1979 | 22.051404291622 | 1978 | 20.299221587014 | 1977 | 20.598888909271 | 1976 | 21.883763115668 | 1975 | 21.240431064404 | 1974 | 24.287766432265 | 1973 | 23.395999575232 | 1972 | 21.318719339086 | 1971 | 21.287123694674 | 1970 | 21.21200183159 |
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