71% (1970)

71% (1971)

64% (1975)

73% (1976)

70% (1974)

66% (1973)

75% (1971)

62% (1973)

72% (1972)

66% (1973)

56% (1973)

70% (1967)

58% (1976)

69% (1976)

65% (1977)

53% (1971)

59% (1975)

58% (1974)

69% (1971)

67% (1975)