Year Number 2000 17000 2001 17000 2002 17000 2003 18000 2004 17000 2005 18000 2006 18000 2007 19000 2008 20000 2009 20000 2010 21000 2011 23000 2012 25000 2013 27000 2014 28000 2015 27000 2016 29000 2017 29000 2018 29000 2019 29000 2020 30000