1970             19.19
1971             13.00
1972             11.31
1973              9.96
1974              8.42
1975              7.50
1976              5.65
1977              6.34
1978              4.58
1979              6.91
1980              4.74
1981              3.22
1982              2.74
1984              2.22
1986              1.10
1988              1.44
1990              1.39
1992              1.16
1995              0.98
1998              0.85