Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 409 | Thousand metric tons | NA |
| 2004 | 549 | Thousand metric tons | 34.23% |
| 2005 | 555 | Thousand metric tons | 1.09% |
| 2006 | 564 | Thousand metric tons | 1.62% |
| 2007 | 564 | Thousand metric tons | 0.00% |
| 2008 | 536 | Thousand metric tons | -4.96% |
| 2009 | 545 | Thousand metric tons | 1.68% |
| 2010 | 557 | Thousand metric tons | 2.20% |
| 2011 | 562 | Thousand metric tons | 0.90% |
| 2012 | 564 | Thousand metric tons | 0.36% |
| 2013 | 570 | Thousand metric tons | 1.06% |
