Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 18298 | Thousand metric tons | NA |
| 2004 | 20478 | Thousand metric tons | 11.91% |
| 2005 | 20960 | Thousand metric tons | 2.35% |
| 2006 | 23308 | Thousand metric tons | 11.20% |
| 2007 | 25750 | Thousand metric tons | 10.48% |
