Year | Value | 2021 | 25.078129137583 | 2020 | 21.253186771917 | 2019 | 23.283004400689 | 2018 | 23.313605927001 | 2017 | 22.290040362878 | 2016 | 21.960375926458 | 2015 | 22.088548816475 | 2014 | 23.412031718882 | 2013 | 25.010136441519 | 2012 | 26.872543228781 | 2011 | 27.551941703865 | 2010 | 26.743766962686 | 2009 | 25.847354113928 | 2008 | 27.764398095445 | 2007 | 28.080217814449 | 2006 | 28.798298867665 | 2005 | 28.203733831672 | 2004 | 27.316968687277 | 2003 | 25.869545808589 | 2002 | 27.134121197204 | 2001 | 26.039313005359 | 2000 | 26.671954474493 | 1999 | 24.254241932058 | 1998 | 23.956953912706 | 1997 | 23.891916519179 | 1996 | 23.936825856759 | 1995 | 23.004906877312 | 1994 | 21.742851984192 | 1993 | 20.736473303164 | 1992 | 20.736496317149 | 1991 | 21.576104909966 | 1990 | 21.304481763954 | 1989 | 20.477650020603 | 1988 | 22.154275663922 | 1987 | 23.628152987837 | 1986 | 25.621227951993 | 1985 | 25.654602935267 | 1984 | 24.53236614635 | 1983 | 24.558719201525 | 1982 | 25.313052618562 | 1981 | 26.250297934594 | 1980 | 25.113815237575 | 1979 | 22.238698911424 | 1978 | 21.819531176324 | 1977 | 22.080572752616 | 1976 | 21.531825065394 | 1975 | 20.385920197383 | 1974 | 20.462298592224 | 1973 | 20.689920571393 | 1972 | 22.951679753764 |
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