Year Number 1995 17173000 1996 17090000 1997 16647000 1998 17352000 1999 17467000 2000 17982000 2001 18180000 2002 18611000 2003 19078000 2004 19374000 2005 19952000 2006 20269000 2007 20773000 2008 21935000 2009 21355000 2010 22004000 2011 23012000 2012 24151000 2013 24813000 2014 25291000 2015 26728000 2016 28121000 2017 29460000 2018 30816000 2019 31884000 2020 15091000