Year	Number
1970	2100
1971	2100
1972	2100
1973	2100
1974	2100
1975	3600
1976	3700
1977	3900
1978	4200
1979	4600
1980	4800
1981	5000
1982	4953
1983	5000
1984	6658
1985	7564
1986	8210
1987	8902
1988	10918
1989	12521
1990	17000
1991	17170
1992	20293
1993	24223
1994	25012
1995	30576
1996	33783
1997	36992
1998	40373
1999	44465
2000	48900
2001	50000
2002	51121
2003	49000
2004	42000
2005	39000
2006	39357
2007	39688
2008	40940
2009	38561
2010	37450
2011	35904
2012	36842
2013	33500
2014	32832
2015	34874
2016	35545
2017	35014
2018	36469
2019	15800
2020	14944
2021	14182