77% (1971)

76% (1970)

79% (1971)

71% (1968)

66% (1972)

73% (1961)

71% (1970)

70% (1972)

77% (1973)

72% (1972)

65% (1974)

73% (1972)

67% (1974)

63% (1973)

67% (1971)

67% (1963)

63% (1965)

58% (1971)

53% (1975)

62% (1969)