Year	Number
1971	6492
1972	7542
1973	7751
1974	8126
1975	8868
1976	9035
1977	9668
1978	10265
1979	11162
1980	12012
1981	12658
1982	13306
1983	15492
1984	15747
1985	17052
1986	17180
1987	17878
1988	18160
1989	18848
1990	19655
1991	20311
1992	21320
1993	22366