Year	Number
1961	11400
1962	11900
1963	12050
1964	14180
1965	15900
1966	16200
1967	16600
1968	17000
1969	17700
1970	19200
1971	20700
1972	21100
1973	25345
1974	23460
1975	28644
1976	31164
1977	33888