1942,4.7
1943,1.9
1944,1.2
1945,1.9
1946,3.9
1947,3.9
1948,3.8
1949,5.9
1950,5.3
1951,3.3
1952,3.0
1953,2.9
1954,5.5
1955,4.4
1956,4.1
1957,4.3
1958,6.8
1959,5.5
1960,5.5
1961,6.7
1962,5.5
1963,5.7
1964,5.2
1965,4.5
1966,3.8
1967,3.8
1968,3.6
1969,3.5
1970,4.9
1971,5.9
1972,5.6
1973,4.9
1974,5.6
1975,8.5
1976,7.7
1977,7.1
1978,6.1
1979,5.8
1980,7.1
1981,7.6
1982,9.7
1983,9.6
1984,7.5
1985,7.2
1986,7.0
1987,6.2
1988,5.5
1989,5.3
1990,5.6
1991,6.8
1992,7.5
1993,6.9
1994,6.1
1995,5.6
1996,5.4
1997,4.9
1998,4.5
1999,4.2
2000,4.0
2001,4.7
2002,5.8
2003,6.0
2004,5.5
2005,5.1
2006,4.6
2007,4.6
2008,5.8