Year | Value | 2021 | 18.302954545455 | 2020 | 18.454545454545 | 2019 | 18.590909090909 | 2018 | 18.75 | 2017 | 18.909090909091 | 2016 | 19.045454545455 | 2015 | 19.204545454545 | 2014 | 19.354545454546 | 2013 | 19.504545454546 | 2012 | 19.654545454545 | 2011 | 19.804545454546 | 2010 | 19.954545454545 | 2009 | 20.106818181818 | 2008 | 20.259090909091 | 2007 | 20.411363636364 | 2006 | 20.563636363636 | 2005 | 20.715909090909 | 2004 | 20.868181818182 | 2003 | 21.020454545454 | 2002 | 21.172727272727 | 2001 | 21.325 | 2000 | 21.477272727273 | 1999 | 21.627272727273 | 1998 | 21.777272727273 | 1997 | 21.927272727273 | 1996 | 22.077272727273 | 1995 | 22.227272727273 | 1994 | 22.377272727273 | 1993 | 22.527272727273 | 1992 | 22.677272727273 | 1991 | 22.827272727273 | 1990 | 22.977272727273 |
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