69% (1987)

73% (1988)

65% (1988)

59% (1978)

61% (1984)

63% (1986)

67% (1988)

66% (1990)

62% (1985)

54% (1980)

62% (1975)

54% (1974)

60% (1984)

63% (1987)

59% (1985)

50% (1985)

63% (1989)

56% (1976)

63% (1984)

53% (1981)