Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 7869 | Thousand metric tons | NA |
| 2004 | 8682 | Thousand metric tons | 10.33% |
| 2005 | 9405 | Thousand metric tons | 8.33% |
| 2006 | 9800 | Thousand metric tons | 4.20% |
| 2007 | 10100 | Thousand metric tons | 3.06% |
