Year Number 1996 32.1608047485352 1998 34.5 2000 29.3532333374023 2002 34.3283576965332 2003 30.348258972168 2004 35.5769233703613 2005 36.8421058654785 2006 27.2727279663086 2007 29.6650714874268 2008 26.4423084259033 2009 30.8056869506836 2010 31.2796211242676 2011 29.577465057373 2012 20.1877937316895 2013 17.8403759002686 2014 28.8461532592773 2015 28.5714282989502 2016 18.5714282989502 2017 21.4285717010498 2018 20.9523811340332 2019 22.8571434020996 2020 23.8095245361328 2021 22.380952835083 2022 23.5849056243896