Year	Number
1985	2800
1989	5000
1990	8000
1991	8000
1992	7000
1993	7000
1994	8000
1995	20000
1996	20300
1997	20850
1998	20850
1999	21150
2000	21200
2001	21200
2002	20900
2003	21400
2004	21000
2005	21000
2006	19000
2007	19000
2008	19000
2009	19460
2010	19460
2011	19460
2012	19460
2013	19460
2014	19460
2015	19460
2016	19460
2017	19000
2018	19200
2019	19000
2020	19000