Year Number 1996 19.5979900360107 1998 29.5 2000 34.825870513916 2002 25.3731346130371 2003 29.3532333374023 2004 31.730770111084 2005 22.9665069580078 2006 16.2679424285889 2007 15.3110046386719 2008 17.7884616851807 2009 14.6919431686401 2010 15.1658763885498 2011 17.3708915710449 2012 20.1877937316895 2013 16.4319248199463 2014 12.9807691574097 2015 17.619047164917 2016 25.7142848968506 2017 26.6666660308838 2018 25.238094329834 2019 23.8095245361328 2020 19.5238094329834 2021 17.619047164917 2022 17.4528293609619