Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 26832 | Thousand metric tons | NA |
| 2004 | 28317 | Thousand metric tons | 5.53% |
| 2005 | 29061 | Thousand metric tons | 2.63% |
| 2006 | 31550 | Thousand metric tons | 8.56% |
| 2007 | 31990 | Thousand metric tons | 1.39% |
