69% (1987)

73% (1988)

65% (1990)

60% (1985)

63% (1986)

64% (1988)

60% (1978)

52% (1982)

66% (1988)

61% (1975)

57% (1972)

63% (1984)

58% (1980)

53% (1981)

54% (1974)

52% (1985)

61% (1984)

64% (1977)

55% (1976)

54% (1980)