Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 934756 | Metric tons, gross weight | NA |
| 2003 | 920514 | Metric tons, gross weight | -1.52% |
| 2004 | 951914 | Metric tons, gross weight | 3.41% |
| 2005 | 850574 | Metric tons, gross weight | -10.65% |
| 2006 | 1000000 | Metric tons, gross weight | 17.57% |
