73% (1975)

69% (1983)

74% (1988)

71% (1989)

70% (1981)

70% (1977)

63% (1980)

65% (1979)

67% (1978)

60% (1976)

73% (1973)

66% (1987)

63% (1980)

64% (1980)

56% (1977)

59% (1979)

58% (1978)

67% (1980)

58% (1977)

62% (1981)