71% (1973)

75% (1972)

73% (1976)

66% (1974)

62% (1973)

69% (1970)

65% (1977)

64% (1975)

58% (1983)

59% (1977)

62% (1980)

60% (1981)

55% (1985)

64% (1984)

63% (1975)

57% (1977)

58% (1976)

62% (1977)

53% (1979)

43% (1986)