Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 18.5650005340576 | Thousand metric tons | NA |
| 2004 | 29.5370006561279 | Thousand metric tons | 59.10 % |
| 2005 | 31.761999130249 | Thousand metric tons | 7.53 % |
| 2006 | 31.8519992828369 | Thousand metric tons | 0.28 % |
| 2007 | 38.5 | Thousand metric tons | 20.87 % |
| 2008 | 40 | Thousand metric tons | 3.90 % |
| 2009 | 30 | Thousand metric tons | -25.00 % |
