Year Number 1996 17.3913040161133 1998 20.1086959838867 2000 16.3043479919434 2002 18.9189186096191 2003 20.5405406951904 2004 20.8955230712891 2005 21.0784320831299 2006 20.5882358551025 2007 21.8446598052979 2008 24.2718448638916 2009 32.5358848571777 2010 33.0143547058105 2011 34.1232223510742 2012 36.0189590454102 2013 36.0189590454102 2014 31.730770111084 2015 27.1428565979004 2016 26.6666660308838 2017 27.619047164917 2018 28.5714282989502 2019 28.0952377319336 2020 30 2021 25.7142848968506 2022 21.2264156341553