Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 248181 | Metric tons, gross weight | NA |
| 2003 | 250490 | Metric tons, gross weight | 0.93 % |
| 2004 | 264492 | Metric tons, gross weight | 5.59 % |
| 2005 | 234881 | Metric tons, gross weight | -11.20 % |
| 2006 | 243350 | Metric tons, gross weight | 3.61 % |
