1991

6.9

1999

7.8

1984

7.1

1981

8.1

2003

8.1

2003

7.5

1996

6.4

1988

6.7

1995

8.1

2001

6.6

2009

6.0

1996

6.0

1996

6.4

1995

7.1

2004

7.0

2006

7.6

1997

8.3

2003

7.2

1997

8.4

2000

7.9