Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 159 | Thousand metric tons | NA |
| 2003 | 220 | Thousand metric tons | 38.36% |
| 2004 | 225.742004394531 | Thousand metric tons | 2.61% |
| 2005 | 220 | Thousand metric tons | -2.54% |
| 2006 | 230 | Thousand metric tons | 4.55% |
| 2007 | 230 | Thousand metric tons | 0.00% |
| 2008 | 230 | Thousand metric tons | 0.00% |
