Year	Number
1976	300
1977	300
1978	400
1979	400
1980	500
1981	500
1982	500
1983	500
1984	600
1985	600
1986	400
1987	900
1988	900
1989	900
1990	900
1991	900
1992	900
1993	900
1994	900
1995	1000
1996	1000
1997	1400
1998	1400