Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 36900 | Thousand metric tons | NA |
| 2004 | 38740 | Thousand metric tons | 4.99% |
| 2005 | 38636 | Thousand metric tons | -0.27% |
| 2006 | 40899 | Thousand metric tons | 5.86% |
| 2007 | 42830 | Thousand metric tons | 4.72% |
