| Year | Value | | 2019 | 2.6222078342506 | | 2018 | 2.5836875664181 | | 2017 | 1.5855880170034 | | 2016 | 0.047207984894029 | | 2015 | 0.47654204980141 | | 2014 | 1.4987396961643 | | 2013 | 1.3323208615212 | | 2012 | 3.1839874634945 | | 2011 | 2.3325315256217 | | 2010 | 2.7794426131259 | | 2009 | 1.753316054276 | | 2008 | 6.8763239367776 | | 2007 | 2.9957203994291 | | 2006 | 3.1149952409795 | | 2005 | 4.1171171171171 | | 2004 | 1.379121380948 | | 2003 | 1.6337139144157 | | 2002 | 0.39138943248532 | | 2001 | 1.792828685259 |
|