Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 24800 | Metric tons | NA |
| 2004 | 25400 | Metric tons | 2.42% |
| 2005 | 26700 | Metric tons | 5.12% |
| 2006 | 28000 | Metric tons | 4.87% |
| 2007 | 29000 | Metric tons | 3.57% |
| 2008 | 30000 | Metric tons | 3.45% |
| 2009 | 31000 | Metric tons | 3.33% |
