1972

3.1

1974

3.8

1982

4.1

2008

4.6

2013

6.5

1981

3.8

1999

3.7

2000

2.6

1968

5.0

1961

4.2

1976

5.6

1972

6.1

1975

5.7

1979

5.3

1967

5.1

1975

2.3

1999

2.9

1974

4.7

1990

4.4

1977

3.5