Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 19437 | Thousand metric tons | NA |
| 2003 | 19655 | Thousand metric tons | 1.12 % |
| 2004 | 20962 | Thousand metric tons | 6.65 % |
| 2005 | 21277 | Thousand metric tons | 1.50 % |
| 2006 | 22540 | Thousand metric tons | 5.94 % |
| 2007 | 22300 | Thousand metric tons | -1.06 % |
| 2008 | 21700 | Thousand metric tons | -2.69 % |
