Year Number 1996 35.5 1998 19.9004974365234 2000 30.348258972168 2002 34.3283576965332 2003 40.2985076904297 2004 41.3461532592773 2005 41.3461532592773 2006 37.019229888916 2007 37.5 2008 39.9038467407227 2009 39.8104248046875 2010 36.4928894042969 2011 35.6807518005371 2012 34.7417831420898 2013 33.8028182983398 2014 30.5418720245361 2015 28.5714282989502 2016 23.645320892334 2017 22.660099029541 2018 18.9320392608643 2019 20.2898559570313 2020 20.2898559570313 2021 19.8067626953125 2022 17.8743953704834