Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 14336 | Thousand metric tons | NA |
| 2003 | 17243 | Thousand metric tons | 20.28 % |
| 2004 | 15690 | Thousand metric tons | -9.01 % |
| 2005 | 17860 | Thousand metric tons | 13.83 % |
| 2006 | 18400 | Thousand metric tons | 3.02 % |
| 2007 | 19480 | Thousand metric tons | 5.87 % |
| 2008 | 19500 | Thousand metric tons | 0.10 % |
