Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 330000 | Metric tons, gross weight | NA |
| 2003 | 500000 | Metric tons, gross weight | 51.52% |
| 2004 | 640000 | Metric tons, gross weight | 28.00% |
| 2005 | 850000 | Metric tons, gross weight | 32.81% |
| 2006 | 1000000 | Metric tons, gross weight | 17.65% |
