20% (1974)

15% (1975)

52% (1973)

33% (1969)

39% (1970)

26% (1968)

43% (1969)

32% (1973)

20% (1970)

41% (1970)

45% (1975)

47% (1971)

37% (1970)

30% (1972)

10% (1971)