Year Number 1996 15.8469944000244 1998 20.7650279998779 2000 17.4863395690918 2002 14.5945949554443 2003 10.2702703475952 2004 6.46766185760498 2005 10.2941179275513 2006 11.7073173522949 2007 16.019416809082 2008 13.1067962646484 2009 11.9617223739624 2010 13.3971290588379 2011 12.7962083816528 2012 11.8483409881592 2013 12.7962083816528 2014 13.942307472229 2015 12.380952835083 2016 13.3333330154419 2017 13.3333330154419 2018 11.9047622680664 2019 12.380952835083 2020 11.4285717010498 2021 12.8571424484253 2022 11.3207550048828