Year Number 1996 35.8695640563965 1998 30.9782600402832 2000 25.543478012085 2002 30.8108100891113 2003 38.9189186096191 2004 31.343282699585 2005 31.8627452850342 2006 32.3529396057129 2007 28.6407775878906 2008 28.1553401947021 2009 25.3588523864746 2010 23.9234447479248 2011 25.5924167633057 2012 23.6966819763184 2013 22.274881362915 2014 22.115385055542 2015 23.8095245361328 2016 22.8571434020996 2017 25.238094329834 2018 23.3333339691162 2019 24.2857151031494 2020 25.7142848968506 2021 28.5714282989502 2022 27.8301887512207