Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1263 | Thousand metric tons | NA |
| 2004 | 1331 | Thousand metric tons | 5.38% |
| 2005 | 1442 | Thousand metric tons | 8.34% |
| 2006 | 1502 | Thousand metric tons | 4.16% |
| 2007 | 1251 | Thousand metric tons | -16.71% |
| 2008 | 1152 | Thousand metric tons | -7.91% |
| 2009 | 1200 | Thousand metric tons | 4.17% |
