Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 7142 | Thousand metric tons | NA |
| 2003 | 8900 | Thousand metric tons | 24.61 % |
| 2004 | 10635 | Thousand metric tons | 19.49 % |
| 2005 | 12183 | Thousand metric tons | 14.56 % |
| 2006 | 13732 | Thousand metric tons | 12.71 % |
| 2007 | 15000 | Thousand metric tons | 9.23 % |
| 2008 | 14918 | Thousand metric tons | -0.55 % |
