| Year |
Price1
(per
metric ton)
|
| 1970 |
$176
|
| 1971 |
184
|
| 1972 |
191
|
| 1973 |
200
|
| 1974 |
248
|
| 1975 |
301
|
| 1976 |
304
|
| 1977 |
331
|
| 1978 |
348
|
| 1979 |
384
|
| 1980 |
430
|
| 1981 |
472
|
| 1982 |
485
|
| 1983 |
465
|
| 1984 |
496
|
|
| Year |
Price1
(per
metric ton)
|
| 1985 |
$500
|
| 1986 |
490
|
| 1987 |
548
|
| 1988 |
601
|
| 1989 |
564
|
| 1990 |
553
|
| 1991 |
530
|
| 1992 |
440
|
| 1993 |
453
|
| 1994 |
466
|
| 1995 |
658
|
| 1996 |
632
|
| 1997 |
546
|
| 1997 |
587
|
| |
|
|