71% (1973)

73% (1976)

69% (1970)

76% (1972)

62% (1973)

66% (1974)

62% (1980)

59% (1977)

63% (1975)

64% (1975)

60% (1981)

65% (1977)

55% (1985)

58% (1976)

58% (1983)

57% (1977)

64% (1984)

43% (1986)

53% (1979)

62% (1977)