Year	Number
1961	137
1962	140
1963	170
1964	200
1965	230
1966	260
1967	290
1968	320
1969	350
1970	380
1971	570
1972	750
1973	939
1974	1000
1975	1075
1976	1140
1977	1210
1978	1280
1979	1350
1980	1400
1981	1450
1982	1500
1983	1500
1984	1550
1985	1600
1986	1650
1987	1700
1988	1750
1989	1800
1990	1830
1991	1850
1992	1850
1993	1850
1994	1850
1995	2000