Year	Number
1961	0.13653483992467041
1962	0.15932521087160262
1963	0.1585820895522388
1964	0.15821312238250348
1965	0.1621120889300602
1966	0.18433179723502305
1967	0.20642201834862386
1968	0.228310502283105
1969	0.24977293369663942
1970	0.2707581227436823
1971	0.29545454545454547
1972	0.3067484662576687
1973	0.3187420314492138
1974	0.32881216605014385
1975	0.3391859537110934
1976	0.35294117647058826
1977	0.36538461538461536
1978	0.37735849056603776
1979	0.4074074074074074
1980	0.4189435336976321
1981	0.43010752688172044
1982	0.42253521126760557
1983	0.41594454072790293
1984	0.40955631399317405
1985	0.4026845637583893
1986	0.4
1987	1.375609756097561
1988	1.3737836290784202
1989	1.8696883852691217
1990	2.3965763195435095
1991	2.9339080459770113
1992	3.4732272069464547
1993	4.02332361516035
1994	4.641475751264505
1995	5.718934911242603