Year	Number
1961	1
1962	1.1428571428571428
1963	1.1428571428571428
1964	1.1428571428571428
1965	1.1428571428571428
1966	1.4285714285714286
1967	2.7777777777777777
1968	5.555555555555555
1969	8.21917808219178
1970	12.564102564102564
1971	12.94871794871795
1972	12.5
1973	11.76470588235294
1974	11.76470588235294
1975	11.76470588235294
1976	11.136363636363637
1977	10.888888888888888
1978	10.208333333333334
1979	9.8
1980	9.8
1981	9.8
1982	9.5
1983	9.5
1984	9.5
1985	9.5
1986	9.5
1987	9.5
1988	9.5
1989	9.3
1990	8.454545454545455
1991	7.75
1992	7.75
1993	7.4399999999999995
1994	6.923076923076923
1995	6.923076923076923
1996	6.923076923076923
1997	7.086614173228346