Year Number 1996 28.4946231842041 1998 30.4812831878662 2000 20.7446804046631 2002 31.7460308074951 2003 35.4497337341309 2004 32.019702911377 2005 40.4878044128418 2006 36.0975608825684 2007 31.5533981323242 2008 33.980583190918 2009 29.6650714874268 2010 33.3333320617676 2011 33.6492881774902 2012 35.5450248718262 2013 39.3364944458008 2014 35.5769233703613 2015 29.5238094329834 2016 26.6666660308838 2017 22.380952835083 2018 21.9047622680664 2019 19.5238094329834 2020 20 2021 18.5714282989502 2022 19.8113212585449