Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 16529 | Thousand metric tons | NA |
| 2004 | 16700 | Thousand metric tons | 1.03% |
| 2005 | 17704 | Thousand metric tons | 6.01% |
| 2006 | 18312 | Thousand metric tons | 3.43% |
| 2007 | 18844 | Thousand metric tons | 2.91% |
