Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 2004 | Thousand metric tons | NA |
| 2004 | 2039 | Thousand metric tons | 1.75% |
| 2005 | 1944 | Thousand metric tons | -4.66% |
| 2006 | 2153 | Thousand metric tons | 10.75% |
| 2007 | 2200 | Thousand metric tons | 2.18% |
