Year	Number
2000	21000
2001	20000
2002	21000
2003	21000
2004	20000
2005	23000
2006	23000
2007	22000
2008	20000
2009	19000
2010	18000
2011	17000
2012	16000
2013	15000
2014	15000
2015	14000
2016	14000
2017	14000
2018	13000
2019	13000
2020	13000