Year	Number
1971	5383
1972	6059
1973	6239
1974	6597
1975	7046
1976	7280
1977	7727
1978	8047
1979	8876
1980	9612
1981	10031
1982	10451
1983	12049
1984	12356
1985	13611
1986	13680
1987	13765
1988	13866
1989	14917
1990	15013
1991	16806
1992	17720
1993	18636
1994	19540
1995	20490
1996	21500
1997	22500