Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1420 | Thousand metric tons | NA |
| 2004 | 1468 | Thousand metric tons | 3.38% |
| 2005 | 1505 | Thousand metric tons | 2.52% |
| 2006 | 1515 | Thousand metric tons | 0.66% |
| 2007 | 1556 | Thousand metric tons | 2.71% |
