Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 835800 | Metric tons, gross weight | NA |
| 2003 | 993000 | Metric tons, gross weight | 18.81% |
| 2004 | 1080993 | Metric tons, gross weight | 8.86% |
| 2005 | 1156168 | Metric tons, gross weight | 6.95% |
| 2006 | 1200000 | Metric tons, gross weight | 3.79% |
