Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1176000 | Metric tons | NA |
| 2004 | 1468000 | Metric tons | 24.83% |
| 2005 | 1566000 | Metric tons | 6.68% |
| 2006 | 1777000 | Metric tons | 13.47% |
| 2007 | 2386000 | Metric tons | 34.27% |
