Year	Number
1971	17289
1972	15925
1973	15354
1974	14674
1975	13293
1976	9536
1977	11248
1978	16915
1979	25805
1980	31030
1981	22497
1982	20433
1983	21040
1984	23192
1985	23714
1986	29124
1987	28181
1988	28001
1989	30079
1990	31556
1991	30360
1992	29019
1993	29320
1996	26620
1997	26690
1999	7548
2000	4353
2001	4888
2002	12333
2003	11382
2004	8407
2005	13104
2007	5428
2008	13778
2009	13450
2010	12369