| Year | *1000 Tons | Year | *1000 Tons | |
| 1971 | 30 | 1988 | 1004 | |
| 1972 | 74 | 1989 | 1081 | |
| 1973 | 490 | 1990 | 1425 | |
| 1974 | 713 | 1991 | 2203 | |
| 1975 | 593 | 1992 | 2937 | |
| 1976 | 567 | 1993 | 3672 | |
| 1977 | 597 | 1994 | 4498 | |
| 1978 | 358 | 1995 | 4696 | |
| 1979 | 605 | 1996 | 5414 | |
| 1980 | 695 | 1997 | 6322 | |
| 1981 | 470 | 1998 | 5602 | |
| 1982 | 712 | 1999 | 6070 | |
| 1983 | 789 | 2000 | 6600 | |
| 1984 | 869 | 2001 | 6916 | |
| 1985 | 813 | 2002 | 7321 | |
| 1986 | 826 | 2003 | 7869 | |
| 1987 | 896 | 2004 | 8682 |
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