Year Number 1996 18.5929641723633 1998 21 2000 24.8756217956543 2002 20.3980102539063 2003 22.8855724334717 2004 25 2005 19.6172256469727 2006 21.0526313781738 2007 25.3588523864746 2008 31.25 2009 29.8578205108643 2010 27.014217376709 2011 23.9436626434326 2012 25.8215961456299 2013 24.8826293945313 2014 18.75 2015 16.1904754638672 2016 16.6666660308838 2017 17.619047164917 2018 17.1428565979004 2019 18.0952377319336 2020 15.2380952835083 2021 16.1904754638672 2022 14.6226415634155