Year	Number
1971	1109
1972	1483
1973	1512
1974	1529
1975	1822
1976	1755
1977	1941
1978	2218
1979	2286
1980	2400
1981	2627
1982	2855
1983	3443
1984	3391
1985	3441
1986	3500
1987	4113
1988	4294
1989	3931
1990	4642
1991	3505
1992	3600
1993	3730
1994	3860
1995	4000
1996	4150
1997	4310