1970    57.5    831.0
 1971    65.4    893.5
 1972    59.7    980.5
 1973    86.1   1098.7
 1974    93.4   1205.7
 1975   100.3   1307.3
 1976    93.0   1446.3
 1977    87.9   1601.3
 1978   107.8   1807.9
 1979   123.3   2033.1
 1980   153.8   2265.4
 1981   191.8   2534.7
 1982   199.5   2690.9
 1983   168.7   2862.5
 1984   222.0   3154.6
 1985   189.3   3379.8
 1986   187.5   3590.4
 1987   142.0   3802.0
 1988   155.7   4075.9
 1989   152.1   4380.3
 1990   175.6   4664.2
 1991   199.6   4828.3