1980

18.9

1990

12.9

2000

29.3

1981

22.5

1991

23.6

2001

34.0

1982

29.9

1992

28.3

2002

16.7

1983

61.9

1993

42.3

2003

24.0

1984

19.1

1994

20.1

2004

17.1

1985

19.6

1995

53.3

2005

51.9

1986

36.0

1996

30.0

2006

34.0

1987

15.4

1997

37.0

2007

12.4

1988

24.4

1998

52.3

2008

29.1

1989

15.9

1999

17.1

2009

17.9