Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5069.40087890625 | Thousand metric tons | NA |
| 2004 | 5371.6982421875 | Thousand metric tons | 5.96% |
| 2005 | 4476.64208984375 | Thousand metric tons | -16.66% |
| 2006 | 4244.52099609375 | Thousand metric tons | -5.19% |
| 2007 | 4784.10498046875 | Thousand metric tons | 12.71% |
