Year	Number
1961	939
1962	1100
1963	1300
1964	1500
1965	1700
1966	1900
1967	2100
1968	2300
1969	2410
1970	2405
1971	2260
1972	2281
1973	1922
1974	1563
1975	1550
1976	1510
1977	1411
1978	1600
1979	1950
1980	1894
1981	1838
1982	1782
1983	1726
1984	1670
1985	1614
1986	1558
1987	1502
1988	1446
1989	1390
1990	1334
1991	1278
1992	1222
1993	1166
1994	1110
1995	1054
1996	998
1997	942
1998	886
1999	830
2000	774
2001	718
2002	662
2003	606
2004	550