72% (1976)

70% (1970)

60% (1981)

65% (1977)

75% (1972)

71% (1973)

58% (1983)

61% (1973)

65% (1975)

66% (1974)

62% (1980)

62% (1977)

64% (1984)

64% (1975)

57% (1977)

58% (1977)

57% (1976)

52% (1969)

55% (1985)

54% (1979)