1975

7.4

1979

7.0

1987

6.3

1996

7.3

2015

7.1

2000

7.1

1997

6.4

2002

6.0

2006

5.8

1990

7.5

2014

5.9

2005

8.1

1999

6.3

2002

7.4

2008

7.1

1993

7.5

1977

7.6

2005

6.1

1981

2.5

2010

5.1

1985

5.0

2002

5.9

2008

6.4