Year	Number
1970	48900
1971	49000
1972	51000
1973	54500
1974	56900
1975	65000
1976	65000
1977	66000
1978	71000
1979	72000
1980	80000
1981	128000
1982	131000
1983	129200
1984	132000
1985	136000
1986	25700
1987	30400
1988	26600
1989	39700
1990	41300
1991	42200
1992	23300
1993	24200
1994	45000
1995	35000
1996	36300
1997	36300
1998	36100
1999	58500