Year Number of 2000 25000 2001 20000 2002 17000 2003 16000 2004 15000 2005 17000 2006 17000 2007 18000 2008 18000 2009 18000 2010 18000 2011 17000 2012 18000 2013 18000 2014 20000 2015 22000 2016 23000 2017 23000 2018 19000 2019 16000 2020 16000