Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 242898 | Metric tons | NA |
| 2004 | 252713 | Metric tons | 4.04% |
| 2005 | 286033 | Metric tons | 13.18% |
| 2006 | 290000 | Metric tons | 1.39% |
| 2007 | 290000 | Metric tons | 0.00% |
| 2008 | 300000 | Metric tons | 3.45% |
