1981

7.4

1999

7.2

2010

6.2

1982

5.2

1993

8.0

1979

6.2

1988

5.2

2009

6.1

1980

6.7

1992

5.3

1989

6.0

2011

7.1

1984

6.5

1990

5.7

1995

6.8

1990

6.6

2011

6.2

1999

5.9

2003

5.6

1980

6.7