Year	Number
1961	8.417508417508419
1962	8.370535714285714
1963	8.32408435072142
1964	8.609271523178808
1965	8.562019758507136
1966	8.73362445414847
1967	9.011943539630836
1968	9.1792656587473
1969	9.452201933404941
1970	9.722222222222223
1971	9.989373007438896
1972	10.887949260042284
1973	11.88222923238696
1974	12.774869109947645
1975	13.4375
1976	14.093264248704662
1977	14.860681114551083
1978	15.503080082135522
1979	16.138917262512766
1980	16.76829268292683
1981	17.391304347826086
1982	18.10865191146881
1983	18.21821821821822
1984	19.073705179282868
1985	18.58275520317146
1986	17.94871794871795
1987	17.19056974459725
1988	16.65034280117532
1989	16.35651322233105
1990	15.949119373776908
1991	15.655577299412915
1992	14.95601173020528
1993	14.16015625
1994	13.398058252427184
1995	12.560386473429952
1996	12.03079884504331
1997	11.025886864813039
1998	9.587727708533079
1999	9.587727708533079
2000	9.587727708533079
2001	9.569377990430622
2002	8.75
2003	9.44
2004	9.555555555555555
2005	10.155555555555555
2006	12.026315789473683