Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 4584 | Thousand metric tons | NA |
| 2003 | 4632 | Thousand metric tons | 1.05 % |
| 2004 | 4494 | Thousand metric tons | -2.98 % |
| 2005 | 5092.8388671875 | Thousand metric tons | 13.33 % |
| 2006 | 5088.8798828125 | Thousand metric tons | -0.08 % |
| 2007 | 5000 | Thousand metric tons | -1.75 % |
| 2008 | 5000 | Thousand metric tons | 0.00 % |
