Year	Number
1960	758
1961	758
1962	758
1963	758
1964	758
1966	758
1967	758
1968	758
1969	758
1970	2200
1971	2200
1972	2200
1973	2200
1974	2200
1975	3400
1976	3800
1977	4900
1978	5200
1979	5600
1980	5870
1981	6360
1982	6999
1983	7445
1984	7894
1985	8141
1986	8300
1987	8500
1988	8700
1989	9109
1990	9272
1991	9871
1992	10258
1993	10503
1994	12453
1995	13743
1996	15353
1997	16404
1998	18114
1999	18891
2000	19991
2001	21669
2002	22399
2003	22975
2004	24040
2005	23954
2006	29925
2007	41686
2008	64738
2009	76336
2010	83383
2011	85354
2012	100537
2013	100500
2014	105300
2015	110000
2016	160848
2017	114352
2019	58000
2020	58000
2021	58000