Year Number 1996 20.7650279998779 1998 18.032787322998 2000 12.021858215332 2002 14.5945949554443 2003 19.4594593048096 2004 20.8955230712891 2005 14.2156858444214 2006 13.1707315444946 2007 9.22330093383789 2008 12.62135887146 2009 12.9186601638794 2010 13.3971290588379 2011 15.1658763885498 2012 8.53080558776855 2013 8.05687236785889 2014 5.28846168518066 2015 5.7142858505249 2016 3.33333325386047 2017 5.2380952835083 2018 3.80952382087708 2019 2.85714292526245 2020 2.38095235824585 2021 3.80952382087708 2022 2.35849046707153