Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 13128 | Thousand metric tons | NA |
| 2004 | 13766 | Thousand metric tons | 4.86% |
| 2005 | 13210 | Thousand metric tons | -4.04% |
| 2006 | 13931 | Thousand metric tons | 5.46% |
| 2007 | 14300 | Thousand metric tons | 2.65% |
