| Year | Value | | 2021 | 19.308126699495 | | 2020 | 21.827381746038 | | 2019 | 29.778266315477 | | 2018 | 29.436514348401 | | 2017 | 29.037057340795 | | 2016 | 27.775285887188 | | 2015 | 29.150249343807 | | 2014 | 35.087375302395 | | 2013 | 36.388100228543 | | 2012 | 36.802753239991 | | 2011 | 37.424273930611 | | 2010 | 34.388435753488 | | 2009 | 29.306841204766 | | 2008 | 30.235913640463 | | 2007 | 25.462435954643 | | 2006 | 21.134488379518 | | 2005 | 20.980341836473 | | 2004 | 21.268567548429 | | 2003 | 20.047673785175 | | 2002 | 17.234811330632 | | 2001 | 16.397583524459 | | 2000 | 14.922852912137 | | 1999 | 14.192466022015 | | 1998 | 14.221671153066 | | 1997 | 15.946757302324 | | 1996 | 13.103246230804 |
|