Year Number 1996 16.5 1998 13.9303483963013 2000 12.93532371521 2002 8.95522403717041 2003 15.4228858947754 2004 15.384614944458 2005 9.61538505554199 2006 8.65384578704834 2007 10.0961542129517 2008 9.13461494445801 2009 8.05687236785889 2010 7.10900497436523 2011 7.0422534942627 2012 6.1032862663269 2013 5.63380289077759 2014 6.40394067764282 2015 3.94088673591614 2016 1.97044336795807 2017 1.97044336795807 2018 0.970873773097992 2019 0.966183602809906 2020 0.966183602809906 2021 1.44927537441254 2022 1.44927537441254