Year | Value | 2022 | 21.143123749713 | 2021 | 20.772185506261 | 2020 | 20.493409239924 | 2019 | 20.605134959998 | 2018 | 19.983117421923 | 2017 | 19.35289741536 | 2016 | 18.67965010361 | 2015 | 18.066227832731 | 2014 | 17.561361855007 | 2013 | 17.112834461363 | 2012 | 16.697299106722 | 2011 | 16.165412483673 | 2010 | 15.657725127788 | 2009 | 15.143216224125 | 2008 | 14.798310369821 | 2007 | 14.488023447999 | 2006 | 14.201576965389 | 2005 | 13.80349912217 | 2004 | 13.497481797314 | 2003 | 13.254819232798 | 2002 | 13.005207590592 | 2001 | 12.779749162148 | 2000 | 12.5860154698 | 1999 | 12.408813219725 | 1998 | 12.264212721966 | 1997 | 12.105231077751 | 1996 | 12.014303771122 | 1995 | 11.939353805049 | 1994 | 11.90514871612 | 1993 | 11.874829073567 | 1992 | 11.860337861366 | 1991 | 11.863614340629 |
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