Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 232 | Thousand metric tons | NA |
| 2004 | 233 | Thousand metric tons | 0.43% |
| 2005 | 234 | Thousand metric tons | 0.43% |
| 2006 | 235 | Thousand metric tons | 0.43% |
| 2007 | 230 | Thousand metric tons | -2.13% |
| 2008 | 378 | Thousand metric tons | 64.35% |
| 2009 | 303 | Thousand metric tons | -19.84% |
| 2010 | 337.5 | Thousand metric tons | 11.39% |
| 2011 | 337.5 | Thousand metric tons | 0.00% |
| 2012 | 337.5 | Thousand metric tons | 0.00% |
