52% (1973)

39% (1970)

33% (1969)

26% (1968)

32% (1973)

15% (1975)

43% (1969)

37% (1970)

41% (1970)

10% (1971)

30% (1972)

20% (1974)

20% (1970)

47% (1971)

45% (1975)