61% (2013)

61% (2009)

55% (1987)

64% (1980)

71% (1981)

71% (1986)

61% (1997)

66% (1996)

66% (2002)

73% (1989)

65% (1995)

55% (1991)

71% (1992)

70% (1984)

61% (1999)

71% (1990)

70% (1999)

55% (1977)

68% (2003)

60% (1980)