Year | Value | 2022 | 21.208575220549 | 2021 | 20.93612093485 | 2020 | 20.701711016096 | 2019 | 21.073429873794 | 2018 | 21.128469843951 | 2017 | 21.07885854699 | 2016 | 21.308970511194 | 2015 | 21.272899529738 | 2014 | 21.183767445933 | 2013 | 21.043149303596 | 2012 | 20.849378055381 | 2011 | 20.426829645596 | 2010 | 20.07987316442 | 2009 | 19.772832399682 | 2008 | 19.424733800274 | 2007 | 19.026348432626 | 2006 | 18.7531627628 | 2005 | 18.578154004642 | 2004 | 18.426732027062 | 2003 | 18.3155478142 | 2002 | 18.45011944395 | 2001 | 18.646220345646 | 2000 | 18.452262851059 | 1999 | 18.225091446616 | 1998 | 17.9958210041 | 1997 | 17.809979946146 | 1996 | 17.636963040686 | 1995 | 17.505300165988 | 1994 | 17.476588332059 | 1993 | 17.470375361442 | 1992 | 17.471413668999 | 1991 | 17.488320040273 |
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