Year	Number
1961	64.52653653815132
1962	67.77893639207507
1963	71.42857142857143
1964	75
1965	75.75387322222765
1966	74.04664938911513
1967	73.85524372230428
1968	71.27583749109053
1969	67.57539483337838
1970	64.75
1971	65.76923076923077
1972	67.17692307692307
1973	69.23076923076923
1974	69.23076923076923
1975	69.23076923076923
1976	69.23076923076923
1977	69.23076923076923
1978	66.53846153846153
1979	65.92307692307692
1980	64.11538461538461
1981	81.92307692307692
1982	75.44444444444444
1983	74.74074074074075
1984	75.44444444444444
1985	75.55555555555556
1986	83.33333333333334
1987	91.4179104477612
1988	101.55952516403079
1989	100.5289006422365
1990	99.52963311382878
1991	98.51949025487257
1992	97.51726712712339
1993	96.5042766827817
1994	95.48855470775614
1995	94.48441247002398
1996	93.48816698515361
1997	92.49633967789165
1998	91.52233363719235
1999	90.54917913700422
2000	89.58031837916064
2001	88.62538744323506
2002	87.68932596367813