Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 31150 | Thousand metric tons | NA |
| 2004 | 32918 | Thousand metric tons | 5.68% |
| 2005 | 31631 | Thousand metric tons | -3.91% |
| 2006 | 30900 | Thousand metric tons | -2.31% |
| 2007 | 31800 | Thousand metric tons | 2.91% |
