Year | Value | 2021 | 17.485303278777 | 2020 | 15.773649731782 | 2019 | 19.809060239194 | 2018 | 19.082826058394 | 2017 | 17.999362120585 | 2016 | 16.143749756907 | 2015 | 14.686304568075 | 2014 | 13.994910485859 | 2013 | 13.297885857998 | 2012 | 12.040804546654 | 2011 | 11.624677745205 | 2010 | 13.396115441819 | 2009 | 11.844036864345 | 2008 | 10.440086408765 | 2007 | 9.7724734037072 | 2006 | 8.7797584102348 | 2005 | 9.1794534213759 | 2004 | 8.9749585001556 | 2003 | 8.6518118525652 | 2002 | 8.5605831408902 | 2001 | 8.8025747473834 | 2000 | 8.7359811113922 | 1999 | 8.4225052333673 | 1998 | 8.6393325466602 | 1997 | 8.7236598660312 | 1996 | 8.7199141868846 | 1995 | 8.9855138587886 | 1994 | 7.7291340479345 | 1993 | 6.6546373561321 | 1992 | 6.4833440723337 | 1991 | 6.6203019361718 | 1990 | 6.9966929682061 |
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