Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 18832.271484375 | Thousand metric tons | NA |
| 2004 | 19603.658203125 | Thousand metric tons | 4.10% |
| 2005 | 18567 | Thousand metric tons | -5.29% |
| 2006 | 19203 | Thousand metric tons | 3.43% |
| 2007 | 20450 | Thousand metric tons | 6.49% |
