Year | Value | 2022 | 25.77708513621 | 2021 | 26.390946051155 | 2020 | 23.839910114207 | 2019 | 24.734550907348 | 2018 | 24.661717683863 | 2017 | 24.042760653929 | 2016 | 23.254841153952 | 2015 | 23.350200186539 | 2014 | 22.729562442517 | 2013 | 22.203774423638 | 2012 | 22.430241712296 | 2011 | 22.950017205269 | 2010 | 22.150322592935 | 2009 | 20.922668852099 | 2008 | 23.529073296402 | 2007 | 24.644776049646 | 2006 | 24.422185972849 | 2005 | 23.750360127454 | 2004 | 23.321360466192 | 2003 | 22.560265746872 | 2002 | 22.887838774751 | 2001 | 23.425789048173 | 2000 | 23.826484351777 | 1999 | 22.789071267513 | 1998 | 22.442119413566 | 1997 | 22.133821806959 | 1996 | 22.130086729497 | 1995 | 22.243176205604 | 1994 | 21.490983186547 | 1993 | 19.980307063333 | 1992 | 20.342441795364 | 1991 | 21.154406752209 | 1990 | 22.129142341095 | 1989 | 22.568029399672 | 1988 | 22.453255308475 | 1987 | 21.475801627008 | 1986 | 22.455727859677 | 1985 | 21.905825875224 | 1984 | 21.595176220394 | 1983 | 20.925312109192 | 1982 | 20.740855478959 | 1981 | 21.124549881641 | 1980 | 22.417082566065 | 1979 | 23.606575383633 | 1978 | 23.73261392387 | 1977 | 23.419441882067 | 1976 | 23.637551130461 | 1975 | 23.376909221527 |
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