1971        41.25   
1972        58.61   
1973        97.81   
1974       159.70   
1975       161.40   
1976       124.80   
1977       148.30   
1978       193.50  
1979       307.80 
1980       606.01  
1981       450.63  
1982       374.18  
1983       449.03  
1984       360.29  
1985       317.30   
1986       367.87
1987       408.91
1988       436.93
1989       381.21
1990       384.07