Year	Number
1961	1600
1962	1800
1963	2000
1964	2200
1965	2400
1966	2600
1967	2870
1968	3280
1969	3950
1970	4274
1971	5097
1972	5167
1973	5058
1974	4761
1975	5136
1976	6669
1977	7135
1978	7658
1979	7888
1980	7430
1981	8009
1982	7974
1983	8909
1984	10211
1985	12000
1986	14500
1987	17000
1988	20000
1989	23000
1990	26000
1991	29000
1992	31200
1993	33725
1994	38926
1995	43295