Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1570 | Thousand metric tons | NA |
| 2004 | 1900 | Thousand metric tons | 21.02% |
| 2005 | 2076 | Thousand metric tons | 9.26% |
| 2006 | 2100 | Thousand metric tons | 1.16% |
| 2007 | 2214 | Thousand metric tons | 5.43% |
