Year | Value | 2022 | 18.836456448709 | 2021 | 18.681003313429 | 2020 | 18.905661027189 | 2019 | 19.371045514669 | 2018 | 19.559418719696 | 2017 | 19.755947229309 | 2016 | 19.976493688529 | 2015 | 20.101404483143 | 2014 | 20.010086526187 | 2013 | 20.927046562857 | 2012 | 20.419414287217 | 2011 | 20.51825666246 | 2010 | 20.240817260691 | 2009 | 20.097364431551 | 2008 | 19.779762978153 | 2007 | 19.253502121744 | 2006 | 18.797882434481 | 2005 | 18.416597391629 | 2004 | 18.066170865866 | 2003 | 17.77574481928 | 2002 | 17.44740325438 | 2001 | 17.218629237574 | 2000 | 17.036074164803 | 1999 | 16.8260651407 | 1998 | 16.545316089087 | 1997 | 16.326616061692 | 1996 | 16.06875313352 | 1995 | 15.860919841 | 1994 | 15.699234013859 | 1993 | 15.528666577335 | 1992 | 15.49050772818 | 1991 | 15.395772589522 |
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