Year Number 1996 27.5 1998 27.8606967926025 2000 24.3781089782715 2002 23.8805961608887 2003 21.3930339813232 2004 18.75 2005 15.865385055542 2006 14.4230766296387 2007 16.3461532592773 2008 17.3076915740967 2009 13.7440757751465 2010 15.6398105621338 2011 14.0845069885254 2012 15.4929580688477 2013 15.962441444397 2014 18.7192115783691 2015 17.7339897155762 2016 14.2857141494751 2017 12.8078813552856 2018 15.5339803695679 2019 14.0096616744995 2020 15.4589376449585 2021 19.8067626953125 2022 18.8405799865723