Year	Number
1961	24.061430676922082
1962	24.8683035342431
1963	26.502627408307276
1964	28.005987566720382
1965	30.569246557345384
1966	34.28507466264005
1967	38.20393129972234
1968	43.66957079425138
1969	50.24971856348403
1970	47.93634548258861
1971	50.50130970955077
1972	53.51429524302687
1973	59.56588483583388
1974	73.0753095276058
1975	74.38641043916112
1976	83.95025317412303
1977	95.21243756760909
1978	109.62862580939137
1979	116.605083493662
1980	144.02650637885233
1981	143.68487287819354
1982	148.46567212734377
1983	148.53659295132167
1984	148.5606389617085
1985	151.8550471429696
1986	151.21088420037577
1987	152.95948757090048
1988	156.91154362705757
1989	159.25031638905529
1990	162.93099939144648
1995	174.99127172437247