69% (1987)

73% (1988)

64% (1988)

62% (1986)

66% (1988)

65% (1990)

59% (1978)

62% (1975)

62% (1985)

53% (1981)

58% (1980)

63% (1987)

62% (1985)

55% (1987)

60% (1985)

62% (1989)

58% (1988)

48% (1983)

50% (1981)

53% (1985)