Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1323 | Thousand metric tons | NA |
| 2003 | 1391 | Thousand metric tons | 5.14 % |
| 2004 | 1265 | Thousand metric tons | -9.06 % |
| 2005 | 1131 | Thousand metric tons | -10.59 % |
| 2006 | 1311 | Thousand metric tons | 15.92 % |
| 2007 | 1300 | Thousand metric tons | -0.84 % |
| 2008 | 1300 | Thousand metric tons | 0.00 % |
