77% (1981)

74% (1977)

71% (1986)

74% (1984)

74% (1976)

66% (1978)

58% (1975)

77% (1979)

57% (1987)

73% (1983)

73% (1984)

65% (1980)

68% (1990)

64% (1983)

66% (1985)

66% (1983)

65% (1988)

68% (1990)

67% (1985)

60% (1989)