2013

6.1

1962

7.0

1963

7.1

1964

7.4

1965

6.7

1967

6.6

1969

6.6

1971

6.4

1974

6.4

1977

6.8

1980

8.2

1979

7.7

1979

6.2

1981

6.5

1983

6.4

1985

6.2

1987

6.5

1989

6.4

1995

6.9

1997

6.4