1954

6.9

1962

8.2

1991

6.4

2002

7.8

1999

7.6

2007

6.4

1990

6.2

1980

5.7

2007

6.0

1986

6.2

1971

7.1

1977

7.0

1989

6.9

1997

5.0

1969

5.0

2013

5.5

2004

6.3

1971

7.5

2006

5.8

2016

6.0