Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4368 | Thousand metric tons | NA |
| 2004 | 4777 | Thousand metric tons | 9.36% |
| 2005 | 5565 | Thousand metric tons | 16.50% |
| 2006 | 6004 | Thousand metric tons | 7.89% |
| 2007 | 6182 | Thousand metric tons | 2.96% |
