Year | Value | 2022 | 19.904101334532 | 2021 | 21.701469495055 | 2020 | 22.109647267269 | 2019 | 21.227706887738 | 2018 | 21.414223950284 | 2017 | 20.547024848917 | 2016 | 19.317767664706 | 2015 | 18.452068442419 | 2014 | 16.770777765389 | 2013 | 16.296242679714 | 2012 | 19.093390700371 | 2011 | 19.192342940948 | 2010 | 19.060890667838 | 2009 | 20.270785978454 | 2008 | 20.315570148621 | 2007 | 21.530442747171 | 2006 | 21.89506771926 | 2005 | 19.665140522326 | 2004 | 21.468438655347 | 2003 | 19.782320864365 | 2002 | 20.560378787595 | 2001 | 20.804545226227 | 2000 | 20.86001483336 | 1999 | 22.505391355641 | 1998 | 22.567387450688 | 1997 | 21.827470252593 | 1996 | 21.304888906737 | 1995 | 20.694126152438 | 1994 | 19.188156354149 | 1993 | 18.849578442323 | 1992 | 16.446261903725 | 1991 | 18.215831968224 | 1990 | 19.822234359387 | 1989 | 19.727713770868 | 1988 | 20.560954474979 | 1987 | 25.744443836242 | 1986 | 20.971307174592 | 1985 | 26.721759785918 | 1984 | 26.342689832385 | 1983 | 28.497829726301 | 1982 | 26.097888384378 | 1981 | 25.351876748177 | 1980 | 26.106911429552 | 1979 | 21.839762874837 |
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