Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 184562 | Metric tons | NA |
| 2004 | 200761 | Metric tons | 8.78 % |
| 2005 | 156853 | Metric tons | -21.87 % |
| 2006 | 157900 | Metric tons | 0.67 % |
| 2007 | 200000 | Metric tons | 26.66 % |
