Year Number 1996 19.0954780578613 1998 21.5 2000 21.8905467987061 2002 19.4029846191406 2003 23.8805961608887 2004 20.1923084259033 2005 21.0526313781738 2006 30.6220092773438 2007 30.6220092773438 2008 26.9230766296387 2009 22.748815536499 2010 25.5924167633057 2011 27.2300472259521 2012 30.5164318084717 2013 32.8638496398926 2014 37.5 2015 35.238094329834 2016 33.3333320617676 2017 33.3333320617676 2018 35.7142868041992 2019 33.8095245361328 2020 38.0952377319336 2021 29.0476188659668 2022 26.4150943756104