Year Number 1996 35.5 1998 15.4228858947754 2000 15.9203977584839 2002 30.348258972168 2003 32.3383102416992 2004 28.8461532592773 2005 23.5576915740967 2006 20.6730766296387 2007 19.7115383148193 2008 21.634614944458 2009 23.222749710083 2010 24.6445503234863 2011 23.0046939849854 2012 20.1877937316895 2013 22.5352115631104 2014 21.674877166748 2015 24.630542755127 2016 22.660099029541 2017 22.660099029541 2018 21.3592224121094 2019 18.8405799865723 2020 19.8067626953125 2021 20.2898559570313 2022 21.7391300201416