Year Number 2007 17866000 2008 16100000 2009 15961000 2010 17741000 2011 20335000 2012 21755000 2013 23988000 2014 22637000 2015 23336000 2016 25226000 2017 27067000 2018 27977000 2019 29346000 2020 11251000