Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 541 | Thousand metric tons | NA |
| 2004 | 566 | Thousand metric tons | 4.62% |
| 2005 | 583 | Thousand metric tons | 3.00% |
| 2006 | 627 | Thousand metric tons | 7.55% |
| 2007 | 638 | Thousand metric tons | 1.75% |
