Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 35242 | Metric tons | NA |
| 2003 | 41667 | Metric tons | 18.23% |
| 2004 | 43971 | Metric tons | 5.53% |
| 2005 | 43595 | Metric tons | -0.86% |
| 2006 | 43600 | Metric tons | 0.01% |
