| Year | Value | | 2022 | 13.814517918648 | | 2021 | 15.863969259072 | | 2020 | 22.143459282177 | | 2019 | 16.616993250474 | | 2018 | 15.448292543329 | | 2017 | 18.19933721397 | | 2016 | 14.883410913857 | | 2015 | 18.880174169191 | | 2014 | 21.926343435439 | | 2013 | 22.14661666769 | | 2012 | 23.098854438337 | | 2011 | 14.595421078779 | | 2010 | 15.906559091997 | | 2009 | 25.01261376566 | | 2008 | 26.326011812907 | | 2007 | 26.384643844538 | | 2006 | 28.623937253874 | | 2005 | 22.630029440628 | | 2004 | 21.353282399547 | | 2003 | 17.958650890564 | | 2002 | 22.290032436827 | | 2001 | 23.539469742684 | | 2000 | 23.978844059535 | | 1999 | 25.744756272189 | | 1998 | 24.082113951868 | | 1997 | 26.18894026451 | | 1996 | 27.519658213071 | | 1995 | 26.032395949572 | | 1994 | 27.086371071606 | | 1993 | 27.663429870273 | | 1992 | 24.494581190032 | | 1991 | 23.567045075284 | | 1989 | 59.361264957342 | | 1988 | 59.015052805351 | | 1987 | 60.203512365115 | | 1986 | 62.548387934842 | | 1985 | 75.694301004601 | | 1984 | 79.739933327024 | | 1983 | 72.96394661709 | | 1982 | 69.915277398196 |
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