Year Number 1996 30 1998 34.3283576965332 2000 33.3333320617676 2002 38.3084564208984 2003 37.3134346008301 2004 32.6923065185547 2005 37.019229888916 2006 39.9038467407227 2007 44.230770111084 2008 42.3076934814453 2009 42.1800956726074 2010 43.1279602050781 2011 43.6619720458984 2012 43.1924896240234 2013 42.2535209655762 2014 41.3793106079102 2015 38.9162559509277 2016 39.4088668823242 2017 37.9310340881348 2018 33.4951438903809 2019 31.4009666442871 2020 28.9855079650879 2021 29.468599319458 2022 29.9516906738281