| Year | Value | | 2019 | 10.090385804431 | | 2018 | 9.6447785034136 | | 2017 | 9.223777502108 | | 2016 | 9.7325124835279 | | 2015 | 11.00201901793 | | 2014 | 13.542630162126 | | 2013 | 14.184762657139 | | 2012 | 14.822719111326 | | 2011 | 16.103412436713 | | 2010 | 16.599947206125 | | 2009 | 18.361079231125 | | 2008 | 25.650149856556 | | 2007 | 21.499160563566 | | 2006 | 23.385169992983 | | 2005 | 17.109117812083 | | 2004 | 18.074570117165 | | 2003 | 17.171580357277 | | 2002 | 15.532811830745 | | 2001 | 29.246675723502 | | 2000 | 28.703382158726 | | 1999 | 16.293971661522 |
|