Year Number 1996 23.3695659637451 1998 22.2826080322266 2000 21.7391300201416 2002 14.5945949554443 2003 17.8378372192383 2004 17.412935256958 2005 20.5882358551025 2006 22.5490188598633 2007 22.3300971984863 2008 20.8737869262695 2009 26.3157901763916 2010 27.2727279663086 2011 27.962085723877 2012 27.014217376709 2013 25.5924167633057 2014 17.3076915740967 2015 18.0952377319336 2016 19.0476188659668 2017 20.4761905670166 2018 26.1904754638672 2019 24.2857151031494 2020 22.380952835083 2021 24.761905670166 2022 27.8301887512207