Year	Number
1971	47.0266
1983	22.46328
1984	21.82612
1985	21.59572
1986	20.29288
1987	20.71414
1988	20.44303
1989	20.73617
1990	21.57804
1991	22.64746
1992	21.05812
1993	20.20356