Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 166278 | Metric tons, gross weight | NA |
| 2003 | 180851 | Metric tons, gross weight | 8.76% |
| 2004 | 157324 | Metric tons, gross weight | -13.01% |
| 2005 | 172314 | Metric tons, gross weight | 9.53% |
| 2006 | 222000 | Metric tons, gross weight | 28.83% |
