Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2852 | Thousand metric tons | NA |
| 2003 | 3500 | Thousand metric tons | 22.72 % |
| 2004 | 4400 | Thousand metric tons | 25.71 % |
| 2005 | 4600 | Thousand metric tons | 4.55 % |
| 2006 | 4400 | Thousand metric tons | -4.35 % |
| 2007 | 4900 | Thousand metric tons | 11.36 % |
| 2008 | 5000 | Thousand metric tons | 2.04 % |
