Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3579 | Thousand metric tons | NA |
| 2004 | 3574 | Thousand metric tons | -0.14% |
| 2005 | 3600 | Thousand metric tons | 0.73% |
| 2006 | 3700 | Thousand metric tons | 2.78% |
| 2007 | 3900 | Thousand metric tons | 5.41% |
| 2008 | 4000 | Thousand metric tons | 2.56% |
| 2009 | 3600 | Thousand metric tons | -10.00% |
