48% (1974)

58% (1980)

57% (1988)

53% (1980)

57% (1975)

62% (1977)

52% (1981)

52% (1987)

57% (1988)

62% (1988)

52% (1982)

62% (1985)

57% (1972)

55% (1990)

58% (1979)

56% (1971)

59% (1987)

59% (1985)

56% (1988)

55% (1976)