1992

6.2

2006

5.3

2008

6.6

2007

6.5

2005

5.4

2002

5.9

1986

5.8

1999

6.8

2001

6.9

1997

6.8

1932

7.0

1932

7.4

1968

7.1

1987

7.3

1989

7.0

1992

6.7

1998

6.6

1978

7.6

1975

7.8

2002

7.2