Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 28155 | Thousand metric tons | NA |
| 2003 | 26639 | Thousand metric tons | -5.38 % |
| 2004 | 28763 | Thousand metric tons | 7.97 % |
| 2005 | 32458 | Thousand metric tons | 12.85 % |
| 2006 | 36200 | Thousand metric tons | 11.53 % |
| 2007 | 38400 | Thousand metric tons | 6.08 % |
| 2008 | 40000 | Thousand metric tons | 4.17 % |
