Year	Number
1961	0.5263157894736842
1962	0.5263157894736842
1963	0.5263157894736842
1964	0.7894736842105263
1965	0.7894736842105263
1966	0.7894736842105263
1967	1.0526315789473684
1968	1.0526315789473684
1969	1.3157894736842104
1970	1.3157894736842104
1971	1.5789473684210527
1972	1.5789473684210527
1973	1.8421052631578945
1974	1.8421052631578945
1975	2.368421052631579
1976	2.368421052631579
1977	2.8947368421052633
1978	2.8947368421052633
1979	3.421052631578948
1980	3.421052631578948
1981	3.9473684210526314
1982	3.9473684210526314
1983	4.2105263157894735
1984	4.736842105263158
1985	5.263157894736842
1986	5.7894736842105265
1987	6.315789473684211
1988	6.5
1989	6.75
1990	7.073170731707316
1991	7.560975609756097
1992	8.048780487804878
1993	8.536585365853659
1994	9.024390243902438
1995	9.285714285714286
1996	9.761904761904763
1997	9.772727272727273
1998	10.227272727272728
1999	10.454545454545453
2000	10.909090909090908
2001	10.869565217391305
2002	11.063829787234042
2003	11.48936170212766
2004	11.666666666666666