Year | Value | 2021 | 18.669913419913 | 2020 | 18.672077922078 | 2019 | 18.674242424242 | 2018 | 18.676406926407 | 2017 | 18.678571428571 | 2016 | 18.680735930736 | 2015 | 18.691558441558 | 2014 | 18.694372294372 | 2013 | 18.697186147186 | 2012 | 18.7 | 2011 | 18.702813852814 | 2010 | 18.705627705628 | 2009 | 18.692316017316 | 2008 | 18.679004329004 | 2007 | 18.665692640693 | 2006 | 18.652380952381 | 2005 | 18.639069264069 | 2004 | 18.625757575758 | 2003 | 18.612445887446 | 2002 | 18.599134199134 | 2001 | 18.585822510822 | 2000 | 18.572510822511 | 1999 | 18.458874458875 | 1998 | 18.345238095238 | 1997 | 18.231601731602 | 1996 | 18.117965367965 | 1995 | 18.004329004329 | 1994 | 17.890692640693 | 1993 | 17.777056277056 | 1992 | 17.66341991342 | 1991 | 17.549783549783 | 1990 | 17.436147186147 |
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