1979

8.3

2002

7.6

2004

7.4

1988

7.5

1997

7.4

1972

8.7

1974

8.6

1990

7.4

1999

7.6

2002

6.1

2003

6.0

1993

5.0

1997

7.6

2003

6.1

2007

7.3

1974

6.3

1969

6.3

2001

5.7

2013

2.5

1983

7.8