71% (1970)

72% (1972)

73% (1976)

65% (1975)

71% (1971)

70% (1967)

53% (1971)

62% (1973)

62% (1972)

69% (1971)

69% (1976)

56% (1973)

70% (1974)

66% (1975)

67% (1973)

70% (1974)

74% (1971)

66% (1973)

58% (1976)

45% (1974)